Gornell University Library Ithaca, New York RETURN TO ALBERT R. MANN LIBRARY ITHACA, N. Y. iT Cornell University The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924001360399 BRITISH DIATOMACEZ. Rennes Section I. FRUSTULES NAKED. Family I. NAVICULEZ. » Frustules free, solitary, more or less elongated, straight or curved; extremities symmetrical. Valve more or less convex, straight or sigmoid, and divided into two equal halves by a longitudinal median line having a central and terminal nodules ; surfaces of the valve on both sides of the median line covered partially or completely with hemi- spherical nodules arranged in transverse, oblique, or longi- tudinal lines, so as to form série, which are either granular . . or costate, according to the aggregation or segregation of the nodules. The original researches of Mr. Wenham®*, recently con- firmed by the more complete observations of the Rev. J. B. Readet, have demonstrated that the markings on the valves of the Naviculee are produced by hemispherical nodules projecting from the surfaces of the valve and arranged in lines inclined at varying angles to its longitudinal axis and to each other; the siliceous hemispheres on the a) * Quart. Micr. Journ, vol. iii. p. 244, and Trans. Micr. Soe. n. s. vol. viii. p. 145. + Monthly Micr. Journ. July 1869, 4 NAVICULEA. vary much in size in different species, from being so minute (in N. rhomboides and others) as to be only visible with the highest magnifying-powers, to being large and distinctly visible with a low power (as in N. pretexta, N. granulata, &c.). The degree of segregation and of aggre- gation of the granules forming the striz is also, in different species, subject to great variation. In N. granulata and others they are widely separated by a distinct interval be- tween them; in N. nobilis and its allies, on the contrary, they are so closely packed as to present the appearance of smooth ridges or costz on the surface of the valve. Be- tween these opposite types every possible intermediate degree of variation prevails in different species, so that no definite limit can be drawn to separate the species with visibly granular striz from those whose striz are apparently costate. Consequently the genus Pinnularia of Ehren- berg, as reconstructed by the late Professor Smith*, must necessarily be abolished, not having been founded on any structural peculiarity which is more than purely specific. Undoubtedly the construction of this genus, and its adop- tion by several observers, has had the pernicious effect of separating species closely allied, and placing them in different genera, thus creating much confusion in the nomenclature of the subject. In numerous instances both Ehrenberg and Smith disregarded the distinction they had drawn between Navicula and Pinnularia in the classifi- cation of certain species. In the present work the latter genus has been reduced to a synonym of the former. In this respect the example of Prof. Kiitzing, M. De Brébisson, aud Mr. Ralfs has been followed. * Synop. of the British Diatomacese, vol. i. p. 54. NAVICULA LITTORALIS. 5 Section I. Vatve BROAD, FLATTENED. Subsection I. Valve elliptical or oval ; strice interrupted. A. Extremities rounded ; strie reaching to the median line, but crossed or interrupted on each side of it by a longitudinal line, or two lines, extending between the apices of the valve. Navicula hyalina, Donkin. Navicula hyalina, Donk. Quart. Micr. Journ. vol. i. n. 8. p.10, pl. i. fig. 6 ; Rabenh. Europ. Diat. p. 181. Plate I. fig. 1. V. linear-elliptical ; strize very fine, indistinct or obsolete ; median line broad, tapering towards the central and terminal nodules, and bordered on either side by a doubly incurved longitudinal line; terminal nodules elongated, narrow. The hyaline valve with striz so delicate that they can be resolved only with extreme difficulty, even in dry specimens, together with the peculiar elongated, terminal nodules, appearing as if inserted into a cleft of the median line, are characters sufficiently distinguishing this species. Hab. Marine. Coast of Northumberland, on the sands between tide-marks, at Cresswell and Boulmar. Navicula littoralis, Donkin, n. sp. Plate I. fig. 2. V. oval; strize slightly inclined, close, very fine, distinct, and crossed near to their inner ends by a straight lon- gitudinal line, nearly parallel with the median line; dry valve yellowish brown. This species is closely allied to N. estiva, but readily 6 NAVICULEX. distinguished from it by its much smaller size, oval shape, much closer and finer strie, by the straight longitudinal line crossing them, and by the colour of the dry valve. Hab. Marine. Abundant in several localities on the sandy beach of Northumberland. Navicula estiva, Donkin. Navicula estiva, Donk. Trans. Micr. Soe. n. 8. vol. vi. p. 32, pl. iii. fig. 18; Ralfs, in Prit. Inf. p. 899; Rabenh. Europ. Diat. p. 184. Plate I. fig. 3. Frustule large. V. elongate-elliptical ; strice fine, distinct, obscurely granular, subparallel, and crossed near the median line by a slightly incurved longitudinal line. This species is distinguished from N. Smithi, Bréb., with which it is generally associated, by its more graceful form and much finer and much less granular strie; dry valve blue. Hab. Marine. On the sandy ripples of the sea-shore (plentiful) at Cresswell, Northumberland; South Shields (A. S. D.). Hull (Mr. Norman); New Brighton (Mr. Comber). Navicula Smithii, De Brébisson. Navicula Smithii, Bréb. in Smith’s Synop. vol. ii. p. 92; Ralfs, in Prit. Inf. p.898; Rabenh. Europ. Diat. p. 178. Navicula elliptica, Smith, Synop. vol. i. p. 48, pl. xvii. fig. 152. Navicula didyma, var., Smith, Synop. vol. i. p. 53, pl. xvii. fig. 154%, Plate I. fig. 4. Frustule large. V. oblong, linear-elliptical, with broadly NAVICULA ELLIPTICA. 7 rounded extremities, sometimes slightly constricted in the middle with broad subcuneate extremities; strize connivent, coarse, granular, about 18 in -001”, inter- rupted near to the median line by a gently incurved longitudinal line. Hab. Marine. Abundant in the sandy ripples on the sea-shore; Cresswell, Boulmar, and Tynemouth, North- umberland; South Shields (4. S. D.). Glenshira sand (Prof. Gregory). Navicula fusca, Gregory. Navicula Smithit, vax. fusca, Greg. Diat. of the Clyde, p.14, pl. i. fig. 15. Navicula fusca, Ralfs, in Prit. Inf. p. 898; Rabenh. Europ. Diat. p. 179. Navicula hyperborea, Grun. in Wien. Verh. 1860, p. 29, t. i. fig. 16, Pinnularia quadrifasciata, Ehren. Mikrogeo, t. xix. fig. 26. Plate I. fig. 5. Frustule large. V. oblong-elliptical, or elongated oval ; striz connivent, very coarse and granular, about 12 in 001", bisected by a longitudinal incurved line; inner section narrow and fainter. This species is readily distinguished from N. Smithii, to which it is closely allied, by its much more elegant figure, coarser striz, larger size, and distinct: brown colour of the valve in balsam, Hab, Marine. Lamlash Bay Isle of Arran, Loch Fyne (Prof. Gregory); stomach of Ascidians near Hull (Mr. Norman). Navicula elliptica, Kiitzing. Navicula elliptica, Kiitz. Bac. p. 98, t. xxx. fig. 55; Rabenh. Europ. Diat. p. 179; Sm. Synop. vol. ii. p. 92; Ralfs, in Prit. Inf. p. 899. Navicula ovalis, Smith, Synop. vol. i. p. 48, pl. xvii. fig. 153. 8 NAVICULER. Pinnularia oides, Rabenh. Stissw. Diat. p. 43, t. vi. fig. 18. Cocconets striata, Ehren, Mikrogeo. t. XV. B. fig. 16? Cocconets finnica, Ehren. Mikrogeo. t. XVII. ii. fig. 19? Plate I. figs. 6a & 68. V. oval, or elliptical, or oblong-elliptical ; strize 27 in 001", distinct, connivent, granular, and crossed by a longi- tudinal incurved line, with a bulging-out opposite the central nodule. Variable in size and outline. Hab. Fresh and brackish water, common. This is one of the few species thriving in either fresh or moderately brackish water; in the latter localities I have found some of the finest specimens. Navicula nitescens, Gregory. Navicula Smithii, var. ntescens, Greg. Diat. of the Clyde, p. 15, pl. i. fig. 16. Navicula nitescens,. Ralfs, in Prit, Inf. p. 898; Rabenh. Europ. Diat. p. 179. Pinnularta Arraniensis, O'Meara, Quart. Mier. Journ. vol. vii. n. s. p- 116, pl. v. fig. 6. Plate I. fig. 7. V. elliptical, attenuated towards the extremities; striae coarse, obscurely granular, about 16 in -001", conver- ging towards the centre, and divided into two nearly equal sections by a longitudinal incurved line parallel with the margin. Hab. Marine. Lamlash Bay Isle of Arran, and Loch Fyne (Prof. Gregory); stomach of Ascidians near Hull (Mr. Norman). Navicula lineata, Donkin. Navicula pao Donk. Trans. Micr. Soc. n. s. vol. vi. p. 82, pl. ili. g. Plate I. fig. 8. V. lincar-clliptical, with a gentle constriction in the middle ; NAVICULA SUBORBICULARIS. 9 striz divided by two longitudinal nearly parallel lines into three nearly equal sections ; the two outer costate and slightly inclined, the innermost faint and granu- lar ; median line broad. Mr. Ralfs (Prit.Infus. p. 899) has doubtfully referred this species to Pinnularia quadrifasciata, Ehren. (Mikrogeo. t. xix. fig. 27), so also has Rabenhorst without qualifica- tion (Europ. Diat.-p. 214). The two species, however, are very dissimilar in their specific characters ; Pin. (Navicula) quadrifasciata belongs to group B of the present sub- section, and is closely allied to N. spectadilis, Greg., differing chiefly in being narrower, and in the narrower sublunate form of the longitudinal unstriated area on each half of the valve. Ehrenberg gives two figures of Pin. quadrifasciata ; but one of them (fig. 25) is undoubtedly N. fusca, Greg. Both forms were discovered by him in the clay marl of Agina, associated with N. pretexta. All three occur together in the Red Sea, from which I possess speci- mens. WN. quadrifasciata has not been found in Britain, nor, to my knowledge, in the north of Europe. — Hab. Marine. In the ripples of the sandy beach be- tween tide-marks (abundant), on the coast of Northumber- land; New Brighton sands (Mr. Comber). Navicula suborbicularis, Gregory. Navicula Smithii, var. suborbicularis, Greg. Diat. of the Clyde, p. 15, pli. fig. 17. Navicula suborbicularis, Ralfs, in Prit. Inf. p. 898. Navicula forcipata, Grev., Rabenh. Europ. Diat. p. 178. Pinnularia forficula, O'Meara, Quart. Micr. Journ. n.s. vol. vii. p. 117, pl. v. fig. 9. Plate I. fig. 9. Frustule small. V. short, broadly oval or suborbicular ; median line broad, bordered by a doubly incurved 10 NAVICULE. line; striae coarse, much inclined, and divided by a doubly incurved longitudinal line into two sections, the inner narrow and faint, the outer broad, conspicuous, and costate, or obscurely granular. Hab. Marine. Lamlash Bay Isle of Arran (Prof. Gre- gory). Navicula pygmza, Kiitzing. Navicula pygmea, Kitz, Spec. Alg. p.77; Rabenh. Siissw. Diat. p. 39, and Europ. Diat. p. 184; Sm. Synop. vol. ii, p.91; Ralfs, in Prit. Inf. p, 899, Navicula minutula, Smith, Synop. vol. i. p. 48, pl. xxxi. fig. 274, Plate I, fig. 10. Frustule minute. V. elliptical or oblong-elliptical, hyaline ; median line faint; striz indistinct, very fine (80 in 001", Smith), and crossed by a faint, doubly incurved longitudinal line. Hab. Brackish water, frequent. B. Extremities rounded or produced; strie@ on each half of the valve separated into two bands (a marginal and a median) by an unstriated longitudinal area, extending between the extremities of the valve ; median band narrow and interrupted by the central nodule. 1. Extremities rounded. Navicula pretexta, Ehrenberg. Navicula pretexrta, Uhr. Berlin, 1840, p. 20; Kiitz. Bac. p. 98; Greg. Diat. of the Clyde, p. 9, pl. i. fig. 11; Ralfs, in Prit. Inf. p. 898 ; Rabenh. Europ. Diat. p. 183. Pinnularia pretexta, Ehr. Mikrogeo, t. xix. fig. 28, Plate II. fig. 1. Frustule large. V. broad-oval ; striz coarse, granular, 8 to 10 in 001"; marginal band narrow, with an inde- NAVICULA HENNEDYII. il finite inner border; median band narrow, close to the median line, and with an indefinite outer border ; unstriated area broad, semilunate, and covered with irregularly scattered, conspicuous granules. Hab. Marine. Lamlash Bay Isle of Arran, Loch Fyne (Prof. Gregory). Discovered by Ehrenberg in the clay- marl of Agina, one of the oldest deposits in which the remains of diatomes have been found. Navicula nebulosa, Gregory. Navicula nebulosa, Greg. Diat. of the Clyde, p. 8, pl. i. fig. 8; Ralfs, in Prit. Inf. p. 898; Rabenh. Europ. Diat. p. 179. Plate IL. fig. 2. V. oval, with a slight tendency to angularity in the middle, and to acumination at the apices; strie fine, granu- lar, rather faint; marginal band narrow, and of even width throughout; median band narrow, linear, and contiguous to the median line; unstriated area semi- lunate. A much more finely striated species than N. Hennedyii. Hab. Marine. Lamlash Bay Isle of Arran (Prof. Gre- gory). Navicula Hennedyii, Smith. Navicula Hennedyii, 8m. Synop. vol. ii. p. 93; Greg. Trans. Micr. Soc. vol, iv. pl. v. fig.3; Ralfs, in Prit. Inf. p. 898, pl. vii. fig. 69 ; Rabenh. Europ. Diat. p. 178. Plate II. fig. 3. V. oval; striz granular, distinct, about 24 in -001"; mar- ginal band with a crescentic inner border and gradu- ally narrower towards the extremities, median band 12 NAVICULEZ. tapering towards the central nodule; unstriated area narrow, lunate. Hab. Marine. Frith of Clyde, January 1854 (Mr. Hennedy) ; Pool Bay (Prof. Smith); Lyme Regis (Mr. Capron) ; Glenshira sand and Lamlash Bay Isle of Arran (Prof. Gregory). Navicula forcipata, Greville. Navieula forcipata, Grev. Quart. Micr. Journ. vol. vii. p. 83, pl. vi. figs. 10 & 11; Ralfs, in Prit. Inf. p. 897; Rabenh. Europ. Diat, p. 178. Plate IT. fig. 4. Frustule small. V. elliptical; striz fine, granular, about 35 in ‘001”; marginal band broad in the middle, gradually tapering towards the extremities, and having a bicrescentic inner border ; median band contiguous to the median line, and with a convex outer border ; unstriated area narrow, incurved at the extremities and middle; dry valve brown. Hab. Marine. Lamlash Bay Isle of Arran (Dr. Gre- ville) ; common on the sandy beach of the coast of North- umberland (A. 8. D.) ; near Hull (Mr. Norman). . Navicula spectabilis, Gregory. Navieula spectabilis, Greg. Diat. of the Clyde, p. 9, pl. i. fig. 10; Ralfs, in Prit. Inf. p. 898; Rabenh. Europ. Diat. p. 178. Plate Il. fig. 5. Frustule large. V. broad, elliptical ; striz coarsely granu- lar, about 22 in 001"; marginal band with a doubly crescentic inucr border, broad in the middle and gradually tapering towards the extremities, median NAVICULA ABRUPTA. 13 band linear, narrower towards the apices; unstriated area bilunate. Hab. Marine. Lamlash Bay Isle of Arran and Loch Fyne (Prof. Gregory). Navicula abrupta, Gregory. Nivicula Lyra, var. abrupta, Greg. Diat. of the Clyde, p. 14, pl. i. fig. 14 ; Rabenh. Europ. Diat. p. 178. Navicula lyra, Sm. Synop. vol. ii. p. 93, pl. xvii. fig. 152a*. Plate II. fig. 6. V. elongated, oval; strie grannular, about 24 in -001"; marginal band broad in the middle, tapering towards the extremities, with a bicrescentic inner border, median band with a convex outer border; unstriated area narrow, incurved in the middle and at the extre- mities; dry valve colourless. In some specimens the extremities of the unstriated longitudinal area reach near to the apices of the valve, in others they terminate abruptly some distance from them ; in this respect considerable variation is observed. I have, without hesitation, separated this form from N. Lyra, Ehren., with which it has been confounded, but from which it is essentially different ; it never occurs with pro- duced extremities, and the longitudinal unstriated area is always incurved towards its extremities, not everted as in N. Lyra. Hab. Marine. Lamlash Bay Isle of Arran (Prof. Gre- gory); Poole Bay (Prof. Smith); Estuary of the river Coquet, Northumberland, plentiful (A. S. D.). 14 NAVICULE.E. 2. Extremities produced. Navicula Lyra, Ehrenberg. Navicula Lyra, Ehren. Amer. 1848, p. 131, t. I. i. fig. 9a; Ktitz. Bac. p. 94, t. xxvili. fig. 55; Spec. Alo. p. 74; Sm. Synop. vol. ii. p. 93; Greg. Diat. of the Clyde, p. 13, pl. i. fig. 18; Ralfs, in Prit. Inf. p. 897; Rabenh. Europ. Diat. p. 177. Navicula Gregoriania, Grev. Quart. Micr. Journ. vol. v. p. 10, pl. ili. fig. 7. Plate II. fig. 7. V. linear, elliptical, with produced broad rounded extre- mities, or linear with cuneate or subcuneate extremi- ties ; striz granular, 22 to 24 in ‘001"; marginal band wide, and broadest in the middle; unstriated area narrow, linear, strongly incurved in the middle and everted towards the extremities, which reach to or near the margin of the valve. In this species the marginal band of strize is proportion- ately wider than in the other members of the present group; it is further distinguished by the double lyre-shaped blank space on the surface of the valve. In the variety with cuneate apices, and in short stunted specimens generally, the longitudinal unstriated areas are frequently straight instead of everted towards their unde- veloped extremities, which do not reach to the margin of the valve. Hab. Marine. Salt Pans, Hampshire (Prof. Smith) ; Cumbrae (Dr. Walker Arnott); Isle of Arran and Loch Fyne (Prof. Gregory); Flamboro’ Head (Mr. Norman) ; on the sandy beach, Northumberland, in several localities, abundant (A. S. D.). NAVICULA ROSTRATA. 15 Navicula clavata, Gregory. Navicula clavata, Greg. Trans. Micr. Soc. vol. iv. p. 46, pl. v. fig. 17; Ralfs, in Prit. Inf. p. 898. Navieula Lyra, Rabenh. Europ. Diat. p. 178. Navicula Wrightit, O’Meara, Quart. Micr. Journ. vol. vii. n. s. p. 116, pl. v. fig. 4. Plate II. fig. 8. V. broadly elliptical, extremities produced, broad, and rounded ; striz granular; marginal band broad, and of equal width except near the extremities, where it is abruptly separated from the median band; unstriated area lunate, with everted narrow extremities reaching to the margin of the valve at the base of its apices. Hab. Marine. Lamlash Bay Isle of Arran, Glenshira sand (Prof. Gregory); coast of Northumberland (4. 8. D.). Navicula rostrata, Ehrenberg. Navicula rostrata, Ehren. Berlin, 1840, p. 18; Kiitz. Bac. p. 94, t. iii. fig. 55; Ralfs, in Prit. Inf. p. 901; Rabenh. Siissw. Diat. p. 37, pl. vi. fig. 52, and Europ. Diat. p. 197. Navicula tumens, Sm. Synop. vol. i. p. 52, pl. xvii. fig. 150; Ralfs, in Prit. Inf. p. 900; Rabenh. Europ. Diat.-p. 192. Navicula sculpta, Ehren. Mikrogeo. t. X. i. fig. 5; Ralfs, in Prit. Inf. . 900. Thies ae Rabenh. Europ. Diat. p. 227. Plate II. fig. 9. V. elliptical, gradually attenuated into produced obtuse extremities; strie slightly inclined, granular, about 36 in 001"; marginal band broad, with an indefinite inner border, and much shortened in the middle, on one side of the valve; median band narrow, linear, and bordering the median line, which is narrow; unstri- ated area narrow sublunate, with indefinite margins. There can be no doubt whatever that the synonyms of 16 NAVICULER, this species are those given above, It is somewhat remark- able that it has been described as constituting three dif- ferent species. The late Prof. Smith’s description and figure of N. tumens, Sm., give a very inadequate idea of the arrangement of the strie in this curious form; the peculiar arrangement is not easily observed, except with superior object-glasses and suitable illumination. I have carefully compared British specimens of this species with those of N. rostrata, Ehren., occurring in the Bergmehl of Santa Fiore, and with those of N. sculpta, Ehren., found in the fossil deposit from Franzensbad, and figured in the ‘ Mikrogeologie ;’ and I find them to be perfectly identical. The British and Santa-Fiore specimens are exactly alike, while those of N. sclupta from Franzensbad are larger and have the granular structure of the valve and the peculiar arrangement of the strie much more strongly developed, so as to be distinctly visible even with a mode- rately low power. To this circumstance, and the imperfect instrument employed in 1840, in the description of N. ros- trata, we may, perhaps, attribute the fact of Ehrenberg having described it as constituting two distinct species. Prof. Smith appears to have been unacquainted with N. rostrata. Hab. Brackish water, Newhaven, Sussex (Prof. Smith) ; near Hull (Mr. Norman) ; near Liverpool (Mr. Comber) ; Salt Marsh, Warkworth, Northumberland (A. S. D.). NAVICULA LATISSIMA. 17 Subsection II. Valve elliptical or oval, with produced, obtuse extremities ; stric not interrupted. Navicula granulata, De Brébisson. Navicula granulata, Bréb. MS. ; Donkin, Trans. Micr. Soc. vol. vi. p. 17, pl. iii. fig. 19; Ralfs, in Prit. Inf. p. 903; Rabenh. Europ. Diat. p. 201. Plate III. fig. 1. Frustule large. V. broad, elliptical or linear-elliptical, with produced, broad, rounded extremities (sometimes elongated and constricted in the middle); median line narrow; striz reaching to the median line, some- what shortened around the central nodule, conver- gent, coarse, and widely granular. Dry valve dullish blue. Distinguished from N. latissima and N. humerosa by its much coarser strie. Hab. Marine. This large and beautiful species is very common in the sandy ripples of the sea-shore in many localities; but it does not occur in a living state in the tidal estuaries of our rivers. Navicula latissima, Gregory. Navicula latissima, Greg. Trans. Micr. Soc. vol. iv. n. s. p. 40, pl. v. fig. 4; Ralfs, in Prit. Inf. p. 903, pl. vii. fig. 70; Rabenh. Europ. Diat. p. 201. Pinnularia divaricata, O'Meara, Quart. Micr. Journ. n. s, vol. vii. p. 116, pl. v. fig. 7. Plate IIL. fig. 2. Frustule large. V. broadly oval or elliptical; extremities slightly, not prominently, produced by a gentle constriction, broad and rounded ; striz distinctly gra- c 18 NAVICULE®. nular, convergent, and of unequal length around the centre, reaching to the median line near the extre- mities, then gradually receding from it towards the central nodule, around which they leave an orbicular blank space. Hab. Marine. Lamlash Bay Isle of Arran, Estuary of the Clyde, Glenshira sand (Prof. Gregory). This appears to be a deep-water species, not being found on the beach associated with N. humerosa. Navicula humerosa, De Brébisson. Navicula humerosa, Bréb. in Sm. Synop. vol. ii. p. 98; Ralfs, in Prit. Inf. p. 903; Rabenh. Europ. Diat. p. 201. Navicula quadrata, Greg. Trans. Micr. Soe. n. s. vol. iv. p. 41, pl. y. fig. 5. Navicula crassa, Greg. Quart. Micr. Journ. vol. iii. p. 41, pl. iv. fig. 18? Plate IIT. fig. 3. Frustule large. V. linear-elliptical, somewhat suddenly contracted into produced, broad, flattened apices ; strie very oblique, radiating around the centre, di- stinctly granular, about 25 in 001", reaching near to the median line, but shortened so as to leave a broad blank space opposite the central nodule. Dry valve colourless. This species is very variable in size and outline. In elongated specimens it is frequently constricted in the middle ; it is closely allied to N. latissima and N. granulata, but readily distinguished from it by its very much finer strie, and by its outline near the extremities, which are much more produced. Hab. Marine. Common on the sea-shore in the sandy ripples between tide-marks, and generally associated with N. granulata. NAVICULA MARINA. 19 Navicula brevis, Gregory. Nawicula brevis, Greg. Diat. of the Clyde, p. 6, pl. i. fig. 4; Ralfs, in Prit, Inf. p. 899; Rabenh. Europ. Diat. p. 192. Plate III. fig. 4. Frustule small. V. short, broad, elliptical, slightly con- stricted into produced, broadly rounded extremities ; strie fine, about 85 in -00L", slightly inclined, not reaching to the median line, and much shortened around the central nodule. Hab. Marine. Lamlash Bay Isle of Arran (Prof. Gre- gory) ; Cumbrae (Prof. Walker Arnott). Navicula marina, Ralfs. Navicula marina, Ralfs, in Prit. Inf. p. 903; Rabenh. Europ. Diat. p. 202. Navicula punctulata, Smith, Synop. vol, i, p. 52, pl. xvi. fig. 151. Plate III. fig. 5. V. broadly oval, with very slightly produced, rounded ex- tremities ; striz reaching to the median line, oblique, convergent opposite the centre, about 32 in ‘001", distinctly granular. Hab. Brackish water. Poole Bay-and Seaford, Sussex (Prof. Smith). In brackish water near Hull, rare (Mr. Norman). Brackish water near Liverpool (Mr. Comber). Brackish water, estuary of R. Wansbeck, Northumberland, abundant (A. 8. D.). Although this species is described as marine in the ‘Synopsis’ of Prof. Sinith, I have never found it in purely marine localities, where its congener N. granulata is found. a2 20 NAVICULE. Navicula pusilla, Smith. Navcula pusilla, Sm. Synop. vol. i. p. 52, pl. xvii. fig. 145 ; Ralfs, in Prit. Inf. p. 900; Rabenh. Alg. Sub. no. 1185, and Europ. Diat. p. 198. ; Navicula gastroides, Greg. Quart. Micr. Journ. vol. iii. p. 40, pl. iv. fig. 17. Plate ITI. figs. 6a & 66. Frustule small. V. varying in outline, from suborbicular or broadly oval to elliptical-lanceolate, with produced, broad, truncate extremities; striz reaching to the median line, radiating, granular, stouter, and more distant around the centre. Had. Fresh and slightly brackish water, frequent. Navicula Carassius, Ehrenberg. Navicula Carassius, Ehren. Amer. 1843, p. 130, t. I. ii. fig. 12; Kiitz. Bac, p. 95, t. xxviii. fig. 67; Rabenh. Siissw. Diat. p. 40, t. vi. 57, and Europ. Diat. p. 193; Ralfs, in Prit. Inf. p. 900. Navicula lacustris, Greg. Quart. Micr. Journ. vol. iv. p. 6, pl. i. 23, 8; Ralfs, in Prit. Inf. p. 903; Rabenh. Europ. Diat. p. 200. Plate IL. fig. 7. Frustule minute. V. elliptical, gradually attenuated into produced narrow obtuse extremities; strie reaching to the median line, convergent towards the centre, distinct, granular. A much smaller species than N. pusilla, with much finer striz, and at once distinguished by its narrow produced apices. Hab. Fresh water. River Coquet Northumberland (A. S. D.); Loch Leven (Prof. Gregory). NAVICULA INFLATA, 21 Navicula Semen, Ehrenberg. Navicula Semen, Ehren. Amer. 1843, t. IV. ii. fig. 8; Kiitz. Bac. p. 99, t, xxviii. fig. 49; Rabenh. Siissw. Diat. p. 38, t.v. fig. 2, and Europ. Diat. p. 194; Sm. Synop. vol. i. p. 50, pl. xvi, fig. 141; Ralfs, in Prit. Infus. p. 900. Pinnularia Semen, Ehren. Mikrogeo. t. XTV. fig. 12, t. XVI. iii. fig. 26, t. XVII. ii. fig. 8P Amphiprora navicularis, Ehren. Mikrogeo. t. IIL. i. fig. 10, 11, & iii. fig. 8, t. IV. ii. fig. 16, t. V. i. fig. 10. Plate IIT. fig. 8. V. oblong-elliptical or oval, slightly constricted into broad flattened extremities; striz reaching to the median line, coarse, obscurely granular, convergent, stouter and more distant, but of equal length around the central nodule. Variable in size and outline. It is difficult to say what species is meant by Ehrenberg as Pinnularia Semen, as different species are figured under this name in the ‘ Mikrogeologie,’ one of these only being striated (t. xiv. fig. 12), and apparently identical with Pin. Gastrum (t. xv. A. fig. 23); the other figures are unstri- ated, and none of them are identical with N. Semen of Smith’s Synopsis, which I have adopted as the genuine form, and which is identical with Amphiprora navicularis, Ehren. Mr. Ralfs describes the strie of N. Semen as “ obsolete or apparent,” Prof. Smith as ‘‘ distinct.” Hab. Fresh water, frequent. Peterhead deposit (Prof. Smith); near Hull (Mr. Norman); River Coquet North- umberland (A. S. D.). Navicula inflata, Kiitzing. Navicula mflata, var. 8, Kiitz. Bac. p. 99, t. iii. fig. 36, 3; Sm. Synop. vol. i. p. 50, pl. xvii. fig. 158; Rabenh. Europ. Diat. p. 191. Pinnularia inflata, Rabenh. Siissw. Diat. p. 44, t. v. fig. 10¢. Plate III. fig. 9. Frustule small. V. elliptical, extremities produced, broad 22 NAVICULE ®. and flattened ; striz oblique, reaching to the median line, distinct, much coarser and more distant opposite the central nodule. Hab. Fresh water. Lough Mourne deposit. Navicula Gastrum, Ehrenberg. Pinnularia Gastrum, Ehren. Amer. p. 183, t. TIT. vii. fig. 22, and Mi- krogeo. t. V. i. fig. 12, t. XV. A. fig. 23; Rabenh. Siissw. Diat, p. 44, t. vi. fig. 15. Navicula Gastrum, Kiitz. Bac. p. 94, t. xxviii. fig. 56; Ralfs, in Prit. Inf. p. 900. Navicula varians, Greg. Trans. Micr. Soc. vol. iii. n. s. p.10, pl. ii. figs. ry sii Plate III. fig. 10. Frustule small. V. broad, elliptical, slightly constricted into broad flattened extremities ; strize coarse, costate, reaching to the median line, oblique and parallel, except opposite the central nodule, where they are transverse, shortened, and of unequal length. Ehrenberg’s figure in the ‘ Mikrogeologie,’ of this species as it occurs in the Loch-Mourne deposit, is very charac- teristic. The figure in the present work also represents a specimen from the same deposit. It is easily recognized from N. Semen by the great difference in the character of its striz in the middle of the valve. Hab. Fresh water. Loch-Mourne deposit (A. S. D.); Scotland (Prof. Gregory). Navicula cocconeiformis, Gregory. Navicula cocconeifornus, Greg. Quart. Micr. Journ. vol. iv. p. 6, pl i. fig. 22; Grev. Ann. & Mag. Nat. Hist. 2nd ser. vol. xv. pl. ix. fig. 6; Sm. Synop. vol. ii. p. 92; Ralfs, in Prit. Inf. p. 896; Rabenh. Europ. Diat. pp. 186 & 189. Plate IIL, fig. 11, Frustule small. V. broad, elliptical, and slightly con- NAVICULA ELEGANS. 23 stricted near the broad rounded: extremities; stris slightly connivent, fine, and very delicate, 54 in ‘001", reaching to the median line. Hab. Fresh water. Braemar (Dr. Greville) ; Elgin, Loch Leven, and other localities in Scotland (Prof. Gregory) ; River Coquet Northumberland, April 1869, abundant (4. S. D.). Navicula hebes, Ralfs. Navicula hebes, Ralfs, in Prit. Inf. p. 896; Rabenh. Europ. Diat. p. 189. Navieula obtusa, Sm. Synop. vol. i. p. 50, pl. xvi. fig. 140. Plate II. fig. 12. Frustule small. V.somewhat convex, elongate, elliptical, constricted beneath the dilated, broadly rounded ex- tremities ; striae sharp and distinct, about 35 in ‘001"; nearly transverse, not reaching to the median line, and shortest around the central nodule. Colour pale brown. Hab. Fresh water. Rassay Earth, Marl, Co. Down, Lough-Mourne deposit (Prof. Smith) ; Loch-Oich deposit, Caledonian Canal (A. 8. D.). Navicula elegans, Smith. Navicula elegans, Sm. Synop. vol. i. p. 49, pl. xvi. fig. 187; Ralfs, in Prit. Inf. p. 907; Rabenh. Europ. Diat. p. 182. Plate IV. fig. 1. V. elliptical, attenuated towards the slightly produced, sub- acute or slightly obtuse extremities ; striz radiate and curved, reaching to the median line, but much short- ened around the central nodule, distinct, costate, 24 in :001". 24 NAVICULEE. Hab. Brackish water : frequent. Pool Bay (Prof. Smith) ; Lancashire (Mr. Johnston); near Hull (Mr. Norman) ; R. Blyth, Northumberland (A. S. D.). Navicula subsalina, Donkin. Navicula Amphisbena, var. 8, Smith, Synop. vol. i. p. 51, pl. xvii. fig. 1478; Ralfs, in Prit. Inf. p. 899, pl. ix. fig. 141, non pl. vii. fig. 72; Rabenh. Europ. Diat. p. 191, confusa cum N. Amphisbena. Plate IV. fig. 2. V. elliptical, or elliptical-lanceolate, with produced, obtuse extremities ; striz distinct, about 30 in ‘001", slightly oblique, shortened in the middle, and lengthened to- wards the extremities, so as to leave a broadly lanceo- late median blank space. This species has long been confounded with N. Amphis- bena, of which, on very insufficient grounds, it has been considered a variety peculiar to brackish water; it is, how- ever, essentially different, in its much coarser striz, in the outline of its extremities, and larger size, independently of habitat. The assertion of the late Prof. Walker Arnott (Quart. Micr. Journ. vol. vii. p. 176), that “N. Amphisbena occurs in fresh water, brackish water, and in the sea” (this being the brackish-water, and NM. brevis, Greg., the salt- water variety), appears to me to be purely hypothetical. By careful observation I have been unable to detect the slightest approximation towards an intermediate state be- tween N. Amphisbena and its supposititious varieties ; con- sequently I have, without hesitation, separated the present species from it. Hab. Brackish water: frequent. NAVICULA PALPEBRALIS. 25 Navicula maculosa, Donkin, n. sp. Plate V. fig. 1. Frustule small. V. linear-elliptical, constricted into pro- duced, narrow, tapering, obtuse or subacute apices; striz somewhat coarse, distinctly granular, oblique, connivent, reaching to the median line, but shortened. around the central nodule; dry valve of leaden-blue colour. This species, in outline, resembles N. apiculata, Bréb., but is essentially different in the flatness of its valve and in the character of its striw, the granules of which are large and distinctly segregated, like those of N. granulata, Bréb., to which it is allied. Hab. Marine; generally associated with N. humerosa, Bréb. Linemouth, Northumberland; coast of Jersey (4. 8. D,). Subsection III. Valve oblong-elliptical, or elliptical-lanceolate ; extremities rounded or acute; strice uninterrupted, not reach- ing to the median line. Navicula palpebralis, De Brébisson. Navicula palpebralis, Bréb. in Sm, Synop. vol. i. p. 50, pl. xxxi. fig. 273; Ralfs, in Prit. Inf. fig. 905; Rabenh. Europ. Diat. p. 182. Navicula Barclayana, Greg. Diat. of the Clyde, p. 8, pl. 1. fig. 9; Ralfs, in Prit. Inf. p. 903; Rabenh. Europ. Diat. p. 201. Plate IV. figs. 3a & 36. V. elliptical-lanceolate, extremities acute and slightly mu- cronate ; strie marginal and of nearly equal length (leaving an elliptical, or elliptical-lanceolate, median blank space), oblique, subparallel, costate, about 22 in 001". 26 NAVICULEE. This species is very variable in size and outline. Hab. Marine. By far the most abundant of the littoral Navicule ; it is generally found in suitable localities, on the sandy beach, during the summer months, so that a sand-gathering can scarcely be made without obtaining it. The specimens sent to me from the sands at Dives in Nor- mandy by M. De Brébisson are exactly similar to those found on the Northumbrian shore ; so also are those of N. Barclayana of Prof. Gregory, sent by him to me from the estuary of the Clyde. Navicula angulosa, Gregory. Navicula angulosa, Greg. Trans. Micr. Soe. n. s. vol. iv. p. 42, pl. v. fig. 8; Ralfs, in Prit. Inf. p. 905; Rabenh. Europ. Diat. p. 176. Plate IV. fig. 4. V. elliptical-lanceolate, extremities subacute; striz oblique, marginal, elongated towards the extremities, shortened and angular in the middle, stout, costate, about 20 in -001”; median blank space lanceolate with in- curved sides. Hab. Marine: littoral. Glenshira sand, estuary of the Clyde (Prof. Gregory) ; coast of Northumberland, abun- dant in localities where there is a slight admixture of fresh water (A. 8. D.). Navicula semiplena, Greville. Pinnularia semiplena, Grev.Quart. Micr. Journ. vol.vii. p. 84, pl.vi. fig.12. Navicula angulosa, var. B, Greg. Trans. Micr. Soc. n. s, vol. iv. p. 42, pl. v. fig. 8*. Plate IV. fig. 5. V. linear-elliptical, or elliptical-lanceolate, extremities sub- NAVICULA LATIUSCULA. 27 acute ; strive lengthened towards the extremities and shortened in the middle (so as to leave a lanceolate blank median space), distant, oblique, costate, about 15 in :001". Hab. Marine. Lamlash Bay Isle of Arran, Glenshira sand (Prof. Gregory). Navicula alpina, Smith. Pinnularia alpina, Smith, Synop. vol. i. p. 55, pl. xviii. fig. 168; Ra- benh. Europ. Diat. p. 213. Navicula alpina, Ralfs, in Prit. Inf. p. 906. Plate IV. fig. 6. Frustule large, on M. V. linear with truncate extremities. V. oblong-elliptical, or elliptical-lanceolate, with rounded extremities ; central nodule depressed ; striz shortened around the central nodule, radiate, distant, broad and costate, about 6 or 7 in ‘001". The M. V. of this species is conspicuous from the two longitudinal, parallel lines of transversely elongated gra- nules observable on the connecting zone. Hab. Fresh water, subalpine. Aberdeenshire (Dr. Dickie) ; Ben M‘Dhui (Mr. P. Grant) ; Loch-Oich deposit, Caledonian Canal; Cheviots, Northumberland (A. S. D.). Navicula latiuscula, Kiitzing. Navicula latiuscula, Kiitz, Bac. p. 98, t. v. fig. 40; Ralfs, in Prit, Inf. p- 905; Rabenh, Siissw. Diat. p, 38, t. vi. fig. 61, and Europ. Diat. p. 182. Navicula patula, Sm. Synop. vol. i. p. 49, pl. xvi. fig. 189. Plate IV. fig. 7. Frustule large. V. oblong-elliptical, or elliptical-lanceo- D2 28 NAVICULE. late, with rounded extremities ; striz slightly oblique, close, and delicate, 36 in 001". This species and the preceding are frequently found associated in subalpine localities, especially in lacustrine habitats. Both are abundant in a lacustrine deposit from Loch Oich on the Caledonian Canal, supplied to me by Mr. Hennedy. Hab. Fresh water. North-west of Scotland, frequent ; Loch-Oich deposit, Caledonian Canal (A. S. D.); Marl, Co. Down (Prof. Smith). Subsection IV. Valve oblong, linear-elliptical, or linear, with rounded or cuneate extremities ; strice fine, transverse, reach- ing to the median line. Navicula levissima, Kiitzing. Navicula levissima, Kiitz. Bac. p. 96, t. xxi. fig. 14; Ralfa, in Prit. Inf. p. 895; Sm. Synop. vol. ii. p. 91; Rabenh. Europ. Diat. p. 188. Stauroneis rectangularis, Greg. Quart. Micr. Journ. vol. ii. p. 99, pl: iv. fig. 17. Plate V. fig. 2. Frustule small. V. hyaline, colourless, linear, sometimes slightly inflated in the middle, extremities flattened and slightly rounded; striz fine, delicate, about 50 in ‘001’, transverse, reaching to the median line; median line and nodules distinct. The appearance of a stauros, as delineated in Prof. Gre- gory’s figure, observable on this species when seen by a medium magnifying-power, is deceptive; the strize reach to the central nodule. Hab. Fresh water: frequent. NAVICULA HITCHCOCKII. 29 Navicula dirhynchus, Ehrenberg. Navicula dirhynchus, Ehren. Amer. p. 181, t. III. i. fig. 11; Kiitz. Bac. p. 95, t. xxviii. fig. 48; Rabenh. Siissw. Diat. p. 40, t. vi. fig. 48; Ralfs, in Prit. Inf. p. 901. Naviewa rhynchocephala, Kiitz., var. parva, Rabenh. Europ. Diat. p.196. Plate V. fig. 3. Frustule small. V. hyaline, nearly linear, with a slight constriction beneath the obtuse extremities; striz inconspicuous ; median line dark and conspicuous ; terminal nodules not reaching to the apices. In outline this species has a strong resemblance to N. affinis ; but it is much smaller, and distinguished by the apparent absence of striz. Hab. Fresh water. R. Coquet Northumberland : fre- quent (4. S. D.). Navicula Hitchcockii, Ehrenberg. Navicula Hitchcockit, Ehren. Amer. p. 180; Mikrogeo. t. V. iii. fig. 11; Kiitz. Bac. p. 101; Ralfs, in Prit. Inf. p. 894,-pl. vii. fig. 62. Plate V. fig. 4. V. oblong, linear, margins triundulate, extremities cuneate, slightly incurved, acute; striz fine, transverse, reach- ing to the median line and central nodule. Hab. Fresh water. Loch-Oich deposit, Caledonian Canal (4. 8. D.). I can find no notice of this species having been previously discovered in Europe. 30 NAVICULER. Navicula dubia, Ehrenberg. Navicula dubia, Ehren. Amer. 1848, p. 180, t. II. ii. fig. 8; Kiitz. Bac. p. 96, t. xxviii. fig. 61; Rabenh. Siissw. Diat. p. 40, t. vi. fig. 60; Greg. Quart. Micr. Journ. vol. iv. p. 3, pl. i. fig. 3; Ralfs, in Prit. Inf. p. 902. Navicula Peisonis, Grunow, in Wien. Verh. 1860, p. 544, t. i. fig. 28; Rabenh. Europ. Diat. p. 202. Plate V. fig. 5. Frustule small. V. linear, with slightly produced, narrow, obtuse, or subacute, extremities; margins straight, or slightly triundulate; striz fine, delicate, transverse, reaching to the median line and crossed, near the margin, by a longitudinal line. Distinguished from N. affinis by its much smaller size, finer striz, and suddenly produced, narrow extremities. Hab. Fresh water. Elgin and Loch Leven, Scotland (Prof. Gregory); River Coquet Northumberland (A. 8. D.). Navicula Iridis, Ehrenberg. Navicula Tridis, Ehren, Amer. 1843, p. 180, t. IV. i. fig. 2; Kiitz. Bac. p. 92, t. xxviii. fig. 42; Ralfs, in Prit. Inf. p. 907; Rabenh. Europ. Diat. p. 171. Pinnularia Iridis, Rabenh. Siissw. Diat. p. 42, t. vi. fig. 1. Navicula firma, Sm. Synop. vol. i. p. 48, pl. xvi. fig. 188. Plate V. fig. 6. Frustule large, on M.V. linear, with rounded. extremities. V. linear or linear-elliptical, with rounded extremities and conspicuous terminal nodules; striz fine, about 35 in ‘001", transverse, reaching to the median line, shortened opposite the central nodule, and interrupted near the margin by a series of wavy longitudinal lines. Colour brownish, iridescent. This is a distinct and well-marked species, although by NAVICULA FIRMA. 3l some observers considered a variety of N. firma. I have found it in a living state in gatherings associated with the latter, with N. affinis and N. amphirhynchus. Hab. Fresh water: frequent. River Coquet Northum- berland (A. 8. D.). Navicula firma, Kiitzing. Navicula firma, Kiitz. Bac. p. 92, t. xxi. fig. 10; Ralfs, in Prit. Inf. p. 909. Navicula firma, var. B and y, Sm. Synop. vol. i. p. 48, and vol. ii. p. 90. Navicula amphigomphus, Ehren. Amer. 1843, p. 129, t. IL. i. fig. 8, and Mikrogeo. numer. figs.; Kiitz. Bac. p. 93, t. xxviii. figs. 40 & 41; Rabeuh. Siissw. Diat. p. 38, t. vi. fig. 47, and Europ. Diat. p. 176; Ralfs, in Prit. Inf. p. 908. Pinnularia amphigomphus, Ehren. Amer, t, IL. i. fig. 27, and Mikrogeo. t. xiv. fig. 11? Navieula dilatata, Ehren, Amer. 1848, p. 180, and Mikrogeo. numer. figs,; Kiitz. Bac. p.99; Rabenh. Siissw. Diat. p. 37, and Europ. Diat. p. 173; Ralfs, in Prit. Inf. p. 908, Navicula affinis, var. b, Rabenh. Europ. Diat. p. 196, and var. 8. am- phirhynchus, Grunow, in Wien. Verh. 1860, p. 544, t. iii. fig. 5. Navicula pannonica, Grunow, in Wien. Verh. 1860, p. 541, t. ii. fig. 40, and Rabenh, Europ. Diat. p. 174 ? Plate V. fig. 7. V. linear, with cuneate, subacute, or obtuse extremities, or linear-elliptical, attenuated towards the obtuse extre- mities ; strie fine, granular, about 40 in :001", trans- verse, reaching to the median line, shortened opposite the central nodule, and interrupted by longitudinal wavy lines near the margin; colour brownish. In consequence of being subject to considerable variation in outline, the position of this species is in a state of great confusion. Kiitzing’s typical form was found in the well- known fossil diatomaceous earth from Santa Fiore in Italy ; as it occurs in this deposit its outline is almost linear, with cuneate, obtuse, or subacute, extremities. Ehrenberg, 32 NAVICULEZ. however, had elevated into a species that form of it in which the linear margins and cuneate extremities are most prominent, and into another species the other variety, in which the middle of the valve is more tumid or elliptical ; the former he named N. amphigomphus, the latter N. dila- tata. Between these two forms, however, every degree of gradation is observable; consequently both are synony- mous with Kiitzing’s type. The late Prof. Smith unfor- tunately, in his ‘Synopsis’ (Joc. cit.) , described and figured N. Iridis, Ehren., as the typical N. firma, and referred Kiitzing’s original type to it as a variety, as well as the N. amphigomphus of Ehrenberg. Rabenhorst (Europ. Diat. loc. cit.) first refers N. firma, Kitz., to N. affnis, Ehren., as a var., and afterwards places it amongst the fossil and extra-European species, referring to it as “fossilis in Italia” (p. 226). Should Pinnularia amphigomphus, Ehren. (Mikrogeo.), on further investigation prove to be a species distinct from N. firma, its specific appellation must be retained. Navicula microstoma, Kitzing, is synonymous with his Nav. lata (Bac. p. 92, t. iii. fig. 51); and although con- sidered by Rabenhorst to be identical with N. firma, it is evidently a distinct species. It is distinguished by its larger size and very turgid middle tapering to the subacute extremities, as well as by the series of longitudinal lines crossing the strie being placed about midway between the median line and the margin. To this species should be referred the fine large form occurring in several diatoma- ceous deposits from the United States; of this Mr. Kitton has given a figure and description (‘Science Gossip,’ April 1867, p. 156, fig. 158). The American specimens are very large and beautiful, especially those in my possession from the Cherryfield deposit. Hab. Fresh water: frequent. NAVICULA AFFINIS. 33 Navicula affinis, Ehrenberg. Navicula affinis, Ehren. Amer. 1843, p. 129, t. I. ii. fig. 7, IT. iii. fig. 2, II. iv. fig. 4, II. v. fig. 4, IIL. iii. fig. 8, IV. ii. fig. 6, and IV. v. fig. 10; Kiitz. Bac. p. 95, t. xxviii. fig. 65, and t. xxx. figs. 45 & 46; Sm. Synop. vol. i. p. 50, pl. xvi. fig. 143; Ralfs, in Prit. Inf. p. 902, pl. xii. fig. 82; Rabenh. Siissw. Diat. p. 40, t. vi. fig. 58, and Europ. Diat. p. 196. Navicula ampliata, Ehren. Mikrogeo. t. xv. figs. 832 & 35. Navicula hiber, var. 8, Roper, Quart. Micr. Journ. vol. vi. p. 25, pl. iii. fig. 10. Plate V. fig. 8. V. linear, or linear-elliptical, with a gently incurved con- striction beneath the rounded extremities; striz fine, about 46 in :001", transverse, reaching to the median line, shortened opposite the central nodule, and inter- rupted by a longitudinal line near to and parallel with the-margin. Distinguished from N. firma by its much smaller size, incurved constriction near the apices, and finer striz; this species is not subject to much variation. I cannot agree with Rabenhorst that it is the type to which N. firma and N. amphirhynchus should be referred as varieties, although these species and N. Jridis are closely allied, and present a great similarity in the structure of their valves. Hab. Fresh water: common. Subsection V. Valve suddenly constricted into produced, capitate, subcapitate, linear, or mucronate extremities. The species included in this subsection are readily distinguished from those of Subsection IT. by the sudden, and generally deep, constriction of the valve into produced extremities ; in the latter the constriction is always gradual and tapering and in some instances very slight. Both sub- sections form very natural groups; and it is essential for 34 NAVICULEZ. the easy identification of species that they should be sepa- rated from each other. A. Extremities capitate or subcapitate. 1. Valve elliptical. Navicula amphirhynchus, Ehrenberg. Navicula amphirhynchus, Ehren. Amer. 1843, p. 129, t. II. i. fig.10 &c. ; Kiitz. Bac. p. 95, t. iv. fig. 18, t. xxi. fig. 11, and t. xxviii. fig. 47; Rabenh. Siissw. Diat. p. 40, t. vi. fig. 50; Sm. Synop. vol. i, p. 51, pl. xvi. fig. 142; Ralfs, in Prit. Inf. p. 901, pl. xii. fig. 6. Navicula producta, Smith, Synop. vol. i. p. 51, pl. xvii. fig. 144; Ralfs, in Prit. Inf. p. 902, pl. vii. fig. 66; Grunow, in Wien. Verh. 1860, p. 548, t. ii. fig. 35. Navicula affinis, var. c, Rabenh. Europ. Diat. p. 196, var. a. genuina, Grunow, in Wien. Verh. 1860, p. 543, t. iii. figs. 2a & 6, & 3, Plate V. fig. 9. V. elliptical or linear, with produced capitate extremities ; striz fine, distinct, granular, about 40 in 001", trans- verse in the middle, oblique towards the extremities, reaching to the median line, slightly shortened oppo- site the central nodule, and interrupted midway be- tween the median line and the margin by one or more undulating longitudinal lines. Dry valve yellowish brown. Had. Fresh water: frequent. Navicula spherophora, Kiitzing. Navicula spherophora, Kiitz, Alg. exs. no, 84, Bae. p. 95, t. iv. fig. 17; Sm. Synop. vol. i. p. 52, pl. xvii. fig. 148; Rabenh. Siissw. Diat. p. 40, t. vi. fig. 65a, and Europ. Diat. p. 191; Ralfs, in Prit. Inf. p. 899. Plate V. fig. 10. V. elliptical-lanceolate, deeply constricted into produced, NAVICULA ANGLICA. 35 capitate apices; strie reaching to the median line, transverse in the middle, slightly oblique near the extremities, fine, granular, about 40 in 001". Rabenhorst, in comparing this species with N. Amphis- bena, observes “ Nihilo minus ejus varietas esse mihi vide- tur.” He describes it as having convergent transverse and very delicate longitudinal strie; the latter, however, have no existence. It is a well-marked species, quite distinct from N. Amphisbena, and is by no means so common or generally distributed. I have never met with it in the North of England, where the latter species is common ; nor can I find any record of its occurrence in Scotland. By the kindness of Mr. T. Eulenstein I have been favoured with fine typical specimens from Stuttgart in Germany ; it forms one of his beautiful series of typical species, so highly deserving the attention of microscopists. Hab. Fresh water: not common. Lewes (Prof. Smith) ; near Hull, rare (Mr. Norman). Navicula anglica, Ralfs. Navicula anglica, Ralfs, in Prit. Inf. p. 900; Rabenh, Europ. Diat. p. 193. Navicula tumida, Sm. Synop. vol. i. p. 58, pl. xvii. fig. 146. Plate V. figs. lla & 118. Frustule small. V. elliptical, deeply constricted into pro- duced, short, capitate apices; strize connivent, con- ‘spicuous, obscurely granular, 24 in -001", reaching to the median line. Hab. Fresh water. Bramley near Guildford, Nov. 1850 (Mr. Capron) ; near Hull, rare (Mr. Norman) ; near Liver- pool (Mr. Comber). 36 NAVICULEE. Navicula punctata, Kiitzing. Stauroneis punctata, Kiitz. Bac. p. 106, t. xxi. fig. 9; Sm. Synop. vol. i. p. 61, pl. xix. fig. 189; Ralfs, in Prit. Inf. p. 912; Rabenh. Europ. Diat. p. 245. Stauroptera punctata, Rabenh, Siissw. Diat. p. 50, t. ix. fig. 11. Plate V. fig. 12. V. elliptical, deeply constricted into produced, capitate apices ; striee conspicuous, granular, about 27 in ‘001", oblique, reaching to the median line, shortened oppo- site to the central nodule, so as to leave a stauronei- form, median, blank space. This species has been placed in the genus Stauroneis by Kiitzing, on account of the peculiar shortening of the strie opposite the central nodule ; it is, however, a genuine Navicula, belonging to the present group. Hab. Fresh water: frequent in clear streams. River Coquet Northumberland, April and May (A. 8. D.). Navicula Amphisbena, Bory de St. Vincent. Navicula Amphisbena, Bory, Encycl. Méthod. 1824; Turp. Dict. cl. t. I. 2. figs. 2&9; Ehren. Inf. 1838, p. 178, t. xiii. fig. 7; Kiitz. Bac. p. 95, t. iii. figs. 41 & 42; Rabenh. Siissw. Diat. p. 40, t. vi. fig. 66, and Europ. Diat. p. 191; Sm. Synop. vol. i. p. 51, pl. xvii. fig. 147; Ralfs, in Prit. Inf. p. 899, pl. vii. fig. 72. Navicula ventricosa, Ehren. Abhandlg. d. Berl. Ac. 1830, p. 67. ~ Frustulia depressa, Kiitz. Synops. p. 21, fig. 27, Alg. ag. dule, Dee. 8, 1833. Plate V. fig. 18. V. broad, elliptical, deeply constricted into produced, ro- tund, capitate apices; striz fine, close, about 40 in 001", oblique and slightly curved, reaching to the median line near the extremities, gradually shortened towards the middle of the valve, so as to leave a NAVICULA UNDOSA. 37 broadly lanceolate, median, blank space. Colour yel- lowish brown. Hab. Fresh water: common. Navicula cryptocephala, Kiitzing. Navicula eryptocephala, Kiitz. Bac. p. 95, t. iii. figs. 20 & 26; Sm. Synop. vol. i. p. 58, pl. xvii. fig. 155; Rabenh. Siissw. Diat. p. 39, t. vi. fig. 71, and Europ. Diat. p. 198; Ralfs, in Prit. Inf. p. 901. Plate V. fig. 14. Frustule minute. V. elliptical-lanceolate, deeply con- stricted into produced, short, capitate apices; striz faint, 56 in 001", transverse, reaching to the median . line. Hab. Fresh water. Frequent in mountain-streams. R. Coquet Northumberland, May (A. S. D.). Navicula undosa, Ehrenberg. Navicula undosa, Ehren. Amer. p. 181, t. IL. ii. fig. 10, Mikrogeo. t. XXXIX. iii. fig. 90; Kiitz. Bac. p. 101, t. xxviii. fig. 83; Rabenh. Siissw. Diat. p. 41, t. vi. fig. 56, and Europ, Diat. p. 209; Ralfs, in Prit. Inf. p. 895. Navicula quinquenodis, Grunow, in Wien. Verh. 1860, p. 522, t. i. fig. 33. Plate VI. fig. 1. Frustule small. V. broad, short, elliptical; margins tri- undulate ; extremities produced, broad, subcapitate ; striz transverse, indistinct. Hab. Fresh water: not common. Near Hull (Mr. Norman) ; Whissonsett, Norfolk (Mr. Kitton). 38 NAVICULE. 2. Valve sublinear, with a median sinuous constriction. Navicula incurva, Gregory. Navicula ncurva, Greg. Quart. Micr. Journ. vol. iv. p. 8, pl. i. fig. 26; Ralfs, in Prit. Inf. p. 893; Rabenh. Europ. Diat. p. 203. Navicula? Biblarium?, Ehren. Mikrogeo. t. XVII. i. figs. 8 & 9? Plate VI. fig. 2. Frustule small. V. hyaline, oblong, with incurved mar- gins, and produced, broad, subcapitate extremities ; striz obscure. Hab. Fresh water. River Findhorn, Loch Leven, Scot- land (Prof. Gregory). Navicula binodis, Ehrenberg. Navicula binodis, Ehren. Abh. Berl. 1840, p. 18; Kiitz. Bac. p.100, t, iii. fig. 35; Rabenh. Stissw. Diat. p. 41, t. v. fig. 5, and Europ. Diat. p. 203; Sm. Synop. vol. i. p. 53, pl. xvii. fig. 159; Ralfs, in Prit. Inf. p. 893. Fragillaria? binodis, Ehren. Amer, 1843, p, 127, Plate VI. fig. 3. Frustule minute. V. oblong, divided into two suborbicular lobes by a median sinuous constriction; extremities produced, narrow, nearly linear, obtuse ; strize obscure. Hab. Fresh water: frequent. 8. Valve lanceolate. Navicula rhynchocephala, Kiitzing. Navicula rhynchocephala, Kiitz. Bac. t. xxx. fig. 85; Sm. Synop. vol. i. p. 47, pl. xvi. fig. 182; Ralfs, in Prit. Inf. p. 900, pl. vii. NAVICULA CUSPIDATA. 39 fig. 68; Rabenh. Siissw. Diat. p. 39, t. vi. fig. 68, and Europ. Diat. p. 196. Plate VI. fig. 4. V. elliptical-lanceolate, attenuated into Frustule small. produced, capitate extremities; striz coarse, costate, about 24 in 001", connivent, reaching to the median line. Hab. Fresh water: common. Navicula ambigua, Ehrenberg. Navicula ambigua, Ehren. Amer. 1848, p. 129, t. IL. ii. fig. 9, and Mikrogeo. t. xv. B. fig. 15; Kiitz. Bac. p. 95, t. xxviii. fig. 66, Spec. Alg. p. 75; Sm. Synop. vol. i. p. 51, pl. xvi. fig. 149; Ralfs, in Prit. Inf. p. 902; Rabenh. Siissw. Diat. p. 40, t. vi. fig. 59, and Europ. Diat. p. 192. Plate VI. fig. 5. V. broadly elliptical-lanceolate with produced, narrow, capitate extremities; strie fine, delicate, 36 in 001", transverse, reaching to the median line. Hab. Fresh water: frequent. Navicula cuspidata, Kiitzing. Navicula cuspidata, Kiitz. Bac. p. 94, t. iii. figs. 24 & 387; Sm. Synop. vol. i. p. 47, pl. xvi. fig. 181; Ralfs, in Prit. Inf. p. 9085, pl. xii. fig. 5; Rabenh. Siissw. Diat. p. 87, t. v. fig. 16, and Europ. Diat. p. 170. Plate VI. fig. 6. V. broadly lanceolate, tapering into slightly produced, sub- capitate apices ; striz fine, delicate, 36 in -001", trans- verse, reaching to the median line. Hab. Fresh water : common. ‘40 NAVICULE#. B. Extremities linear or mucronate. Navicula Rostellum, Smith. Navicula Rostellum, Sm. Synop. vol. ii. p. 93; Ralfs, in Prit. Inf. p. 900; Rabenh. Europ. Diat. p. 195. Navicula apiculata, Greg. Quart. Micr. Journ. vol. iv. p. 4, pl. i. fig. 18, Plate VI. fig. 7. Frustule small. V. broadly elliptical-lanceolate, suddenly constricted into produced, linear, short, obtuse apices ; strive indistinct, 80 in ‘001". . Hab. Fresh water. Grasmere, Aug. 1853 (Prof. Smith) ; Falls of Tummel, July 1854 (Dr. Greville) ; Mull earth, Elgin, &c. (Prof. Gregory). Navicula integra, Smith. Pinnularia integra, Sm. Synop. vol. ii. p. 96; Rabenh. Europ. Diat. p. 220. Pinnularia rostrata, Greg. Quart. Micr. Journ. vol. iv. p. 4, pl. i. fig. 14, Navicula integra, Ralfs, in Prit. Inf. p. 895. Plate VI. fig. 8. Frustule minute. V. elliptical-lanceolate, slightly inflated in the middle and suddenly constricted into produced, mucronate apices; striz fine, indistinct, reaching to the median line, stouter and more distant around the central nodule. Hab. Fresh water. Powmouth Ayrshire (Prof. W. Arnott) ; various localities in Scotland (Prof. Gregory) ; River Coquet Northumberland (A. 8. D.). NAVICULA SERIANS 4) Subsection VI. Valve lanceolate ; strie fine, transverse, or slightly oblique, reaching to the median line. Navicula fulva, Nitzsch. Frustulia fulva, Nitzsch (ex parte), Breitage, p. 87, t. iii. fig. 19 (1817). Navicula fulua, Ehren. Inf. 1838, p. 177, t. xiii. fig. 6, Mikrogeo. numer. figs.; Rabenh. Siissw. Diat. p. 37, t. v. fig. 17, and t. vi. fig. 62. Navicula cuspidata, Kiitz. Bac. p. 94; Ralfs, in Prit. Inf. p. 905. var. Rabenh. Europ. Diat. p. 170, Plate VI. fig. 9. V. lanceolate, slightly constricted beneath the obtuse extremities ; striz slightly oblique, fine, about 30 in 001". After a very careful comparison of this form with N. cuspidata, Kiitz., which it closely resembles in general outline, I have considered it necessary to reestablish it as a species by separating it from the latter, from which it differs essentially in its smaller, narrower, and yellowish- brown-coloured valve, with unproduced extremities, coarser and distinctly oblique striz. Hab. Fresh water in subalpine localities. Loch-Oich deposit (A. S. D.). Navicula serians, De Brébisson. Navicula serians, Bréb. in Kiitz. Bac. p. 92, t. xxx. fig. 28; Rabenh. Siissw. Diat. p. 38, t. vi. fig. 51, and Europ. Diat. p. 172; Sm. Synop. vol. i. p. 47, pl. xvi. fig. 180; Ralfs, in Prit. Inf. . 904. Navicula a Ehren, Amer. 1848, t. I. iii. fig. 4, t. IL. vi. fig. 27, and t. IV. i. fig. 6, and Mikrogeo. numer. figs. Navicula punctulata, Ehren. Mikrogeo. t. XVI. i. fig. 1. Plate VI. fig. 10. V. rhomboid-lanceolate, with subacute extremities ; striz E 42 NAVICULEE. transverse, fine, granular, about 60 in ‘OOL", shortened opposite the central nodule. Colour of dry valve brown. The “longitudinal striz,” as they are termed in this species, appear to be produced by plicz or folds on the surface of the valve. Hab. Fresh water: frequent in boggy pools in elevated, exposed, or subalpine localities. Navicula rhomboides, Ehrenberg. Navicula rhomboides, Ehren. Amer. 1848, t. IIT. i. fig. 15; Kiitz. Bac. p. 94, t. xxviii. fig. 45, and t, xxx. fig. 44; Rabenh. Siissw. Diat. p. 38, t.v. fig. 18, and Europ. Diat. p.171; Sm. Synop. vol. i. p. 46, pl. xvi. fig. 129, and vol. ii. p.90; Ralfs, in Prit. Inf. p. 903, Plate VI. fig. 11. V. rhomboid-lanceolate, nearly quadrangular, extremities slightly obtuse, or rounded ; striz fine, indistinct, 85 in ‘001", transverse, reaching to the median line. Hab. Fresh water: frequent, especially in boggy pools in subalpine localities. Navicula crassinervia, De Brébisson. Navicula crassinervia, Bréb. in Sm. Synop. vol. i. p. 47, pl. xxxi. fig. 271; Ralfs, in Prit. Inf. p. 900. Frustulia saxonica, forma aquatica, Rabenh. Europ. Diat. p. 227. Plate VI. fig. 12. Frustule small. V. hyaline, lanceolate, gently constricted beneath the obtuse extremities ; strise obscure. Hab, Fresh water: alpine or subalpine. Snow-mud, Grampians (Dr. Dickie); Cheviots, Northumberland, abun- dant in peat-mosses in exposed situations (4. 8. D.). NAVICULA VENETA. 43 Navicula veneta, Kiitzing. Navicula veneta, Kiitz. Bac. p. 96, t. xxx. fig. 76; Rabenh. Siissw. Diat. p- 39, t. vi. fig. 83; Ralfs, in Prit. Inf, p. 901. Navicula gregaria, Donkin, Quart. Micr. Journ. n. s. vol. i. p. 10, pl. i. fig. 10; Rabenh. Europ. Diat. p. 177. Navicula eryptocephala, var., Rabenh, Europ. Diat. p. 198. Plate VI. fig. 13. Frustule minute. V. broadly lanceolate, with slightly pro- duced subacute apices; strie rather indistinct, fine, connivent, reaching to the median line. This, though minute, is an exceedingly interesting species, in consequence of having the power of locomotion very highly developed. After having been well shook in a bottle and then placed under the microscope, it displays at first great uneasiness and activity ; several individuals may be seen directing their course simultaneously, and as it were voluntarily, towards any extraneous object near them ; to this they soon attach themselves in groups and adhere with wonderful tenacity, remaining at rest when they have once fixed themselves. This highly interesting pheno- menon can be readily observed, as this species is very abundant, and may be collected in large quantities. Hab. Submarine. It is abundant in estuaries and har- bours between tide-marks, especially where small streams pass over the sandy beach into the sea. In such situations it is therefore covered with fresh water for a short period during ebb tide and with salt-water for several hours during the flow. It is not, however, confined to the beach, but frequently forms an olive stratum ou the surface of piers, stones, and piles in our harbours. 44 NAVICULE. Navicula Crucicula, Smith. Stauroneis Crucicula, Sm. Synop. vol. i. p. 60, pl. xix. fig. 192; Ralfs, in Prit. Inf. p. 912, pl. vii. fig. 64; Rabenh. Europ. Diat. p. 261. : Plate VI. fig. 14. V. broadly lanceolate, or elliptical-lanceolate, slightly con- stricted beneath the obtuse apices; striz fine, close, slightly oblique, coarse and distant opposite the central nodule. : The appearance of a stawros, which this species presents, in the middle of the valve, when viewed with a low power, is deceptive; a careful examination with a high power shows the appearance to be produced by a peculiar modi- fication of the strie opposite the central nodule, where they are stout, opaque, and distant. Hab. Brackish water. Belfast Bay, Aug. 1849 (Prof. Smith). Estuary of River Blyth, Northumberland (A. 8. D.). Subsection VII. Valve cruciform ; stric fine, transverse, reaching to the median line, Navicula Follis, Ehrenberg. Navicula Follis, Ehren, Inf. 1888, p. 179; Mikrogeo. t. XVI. i. fig. 14, and ii. fig. 12, t. XVII. i. fig. 15, and ii. fig. 21. Navicula Crux, Ehren. Inf. p, 184. Navicula inflata, Kiitz. Bac. p. 99, t. iii. fig. 36. 1 and 2; Rabenh. Siissw. Diat. p. 41, t. v. fig. 10, and Europ. Diat. p. 191; Ralfs, in Prit. Inf. p. 899. Frustulia inflata, Kiitz, Syn. 1833, t. i. fig. 14. Plate V1. fig. 15. Frustule small. V. cruciform, with incurved sides and NAVICULA FOLLIS. 45 slightly turgid, obtuse apices; strie fine, transverse, distinctly granular, reaching to the median line. Kiitzing refers this form to his N. inflata; but it is evident that under this name he has included two widely different species, one of which (his typical form) he deline- ates as unstriated, the other, which he names the variety, being striated; the latter is the Pinnularia inflata of Rabenhorst (Siissw. Diat.), and apparently identical with Navicula inflata of the ‘Synopsis’ and of the present work, as will be seen by the synonyms I have given of that species. It follows therefore that the typical N. inflata of Kiitzing must be reduced to a synonym of N. Follis. Rabenhorst, more recently (Europ. Diat.), has reunited his P. inflata and N. inflata, Kiitz., with a single descrip- tion for both, representing the striz to be from 26 to 80 in ‘001", and distinctly granular. Mr. Ralfs, on the con- trary, states that the strie are absent or indistinct; he, however, like Rabenhorst, refers N. Follis to the typical N. inflata of Kitzing. I consider N. Follis to be quite distinct from N. Trochus, Ehren. Hab. Fresh water: rare. Near Heigham, Norfolk (Mr. Kitton). I have found it in the Loch-Oich deposit, Cale- donian Canal, from which the specimen figured was obtained. Subsection VIII. Valve divided into two lobes by a median sinuous constriction ; strice reaching to the median line, but divided into two sections by a longitudinal groove. This subsection comprises the genus Diploneis of Ehren- berg. Although an exceedingly natural group, its members are not distinguishable from the Navicule by any decided generic characters. They are all recognized by two essen- 46 NAVICULE. tial features—by the median constriction of the valve and by the division of the strie into an outer conspicuous, and an inner fainter section, by an intersecting longitudinal groove ; this latter character connects them with Division A of Subsection I., in which it is also developed, especially in N. lineata and N. suborbicularis. Navicula Crabro, Ehrenberg. Navicula Crabro, Ehren. in Kiitz. Spec. Alg. p. 83; Sm. Synop. vol. ii, p. 94; Ralfs, in Prit. Inf. p. 804; Rabenh. Europ. Diat. p. 204. Navicula pandura, Bréb. Diat. de Cherb. fig. 4; Greg. Trans. Mier. Soc. n. 8, vol. iv. p. 43, pl. v. fig. 11; Ralfs, in Prit. Inf, 893. Navicula nitida, Greg. Trans. Micr. Soc. n. s, vol. iv. p. 44, pl. v. figs. 12 & 12%, Navicula didyma, costate var., Greg. Trans. Micr. Soc, n.s. vol. iv. p. 45, pl. v. fig. 15. Pinnularia Crabro, Ehren. Berlin, 1844; Rabenh. Europ. Diat. p. 219. Pinnularia pandura, Bréb., var, 8. elongata, Greg. Diat. of the Clyde, p. 17, pl. i. fig. 22. Diploneis Crabro, Ehren. Mikrogeo. t. xix. fig. 29. Plate VII. figs. la & 18. Frustule large. V. panduriform, with cuneate, obtuse extremities ; striz subparallel, nearly transverse, cos- tate, or obscurely granular, coarse, about 11 in ‘001", interrupted by a straight longitudinal groove into a broad outer and a narrow inner section, the latter consisting of a longitudinal row of conspicuous hemi- spherical nodules. No better illustration than this species could be selected to show the necessity for abolishing the genus Pinnularia, and the confusion its establishment has created. It will be seen by the synonyms given that N. Crabro has been placed in the genus Navicula by some observers and in Pinnularia by others, while by others, again, it has been referred to both these genera. It is subject to considerable NAVICULA INTERRUPTA. 47 variation in size and outline; in some specimens an 0d- securely granular appearance of the strie can be observed, or rather the striz present the appearance of being tipped with granules, while in others they appear costate. Fur- ther, I have in certain portions of the valve, especially in very large specimens from the Red Sea, seen a granular appearance, not observable in other portions. After a most careful examination and comparison of numerous specimens from various localities, including those of Pinnularia pandura, Bréb., var. 8. elongata, of Prof. Gre- gory, sent to me by him from the Estuary of the Clyde, I feel convinced that the latter form is the typical N. Crabro of Ehrenberg. The form which Dr. Greville has figured as N. Crabro (Quart. Micr. Journ. vol. v. p. 7, pl. ui. fig. 11), from the West Indies, is, as I have ascertained from authentic specimens, and as believed by Mr. Ralfs, a different and distinct species, for which I suggest the name of N. Gre- villei ; it is smaller than N. Craéro, and distinguished by its compactly granular strie, which radiate from the centre of each lobe, and are much more conspicuous near the margin. Navicula interrupta, Kiitzing. Navicula interrupta, Kiitz. Bac. p. 100, t. xxix. fig. 93; Ralfs, in Prit. Inf. p. 894. Novicula ——, Bailey, in Amer. Journ. of Science, 1842, pl. il. fig. 18. Plate VII. fig. 2. V. divided into two oval or suborbicular lobes by a deep sinuous constriction; strie costate and radiating from the middle of each lobe, outer section coarse and conspicuous ; inner narrow, linear, faint ; intersecting groove straight ; median line broad. This species is readily distinguished from N. Apis, which AS NAVICULES. it much resembles in size and outline, by its conspicuous costate strie radiating from the middle of each lobe. Kiitzing’s figure is very characteristic. Rabenhorst by his description appears to have confounded it with N. Apis. Hab. Brackish water. Estuary of River Coquet, North- umberland (A. S. D.). Navicula Apis, Ehrenberg. Navicula Apis, Ehren. Amer, p. 182, t. III. vii. fig. 18; Kiitz. Bac. p. 100, t. xxviii. fig. 76; Rabenh. Stissw. Diat. p. 46, pl. vi. fig. 28; Ralfs, in Prit. Inf. p. 894. Navicula didyma, var., Sm. Synop. vol. i. p. 58, pl. xvii. fig. 1544’; Ralfs, in Prit. Inf. pl. vii. fig. 61; Rabenh. Europ. Diat. p. 203. Navicula interrupta, Kiitz.; Rabenh. Europ. Diat. p. 205. Plate VII. fig. 3. V. deeply constricted into two oval or suborbicular lobes ; strie nearly transverse, granular, about 26 in ‘001"; outer section conspicuous, inner narrow, faint, and linear; median line broad. The utmost confusion prevails concerning this species, which nevertheless possesses very definite and distinctive characters. The original figures and descriptions of it by Ehrenberg and Kiitzing represent the strize to be parallel and granular, and the valve.to be constricted into two nearly semiorbicular lobes (‘‘media in partes duas fere semiorbiculares constricta, apicibus obtusis, pinnulis aspe- ris”). The late Prof. Smith unfortunately described it and N. interrupta, Kiitz., as synonymous with and constituting an ordinary form of N. didyma, Ehren. Rabenhorst (Europ. Diat.) refers N. Apis to N. didyma as a variety with subparallel strie, and evidently confounds it with N. interrupta, Kiitz., which he erroneously describes as having granular subradiating strie ; this description is not appli- NAVICULA ENTOMON. 49 cable to it, but to N. Apis. Kiitzing’s figure of N. inter- rupta represents it as having costate strie radiating from the middle of each lobe, not granular and parallel as in his and Ehrenberg’s figures of N. Apis. Hab. Brackish water: frequent. Estuary of River Co- quet, Northumberland (4. S. D.). Navicula incurvata, Gregory. Navieula incurvata, Greg. Trans. Micr. Soc. n. 8. vol. iv. p. 44, pl. v. fig. 13; Ralfs, in Prit. Inf. p. 893. Navicula splendida, Greg., var., Rabenh. Europ. Diat. p. 204. Navicula interrupta, Kiitz., Grunow, in Wien. Verh. 1860, p. 531, t. iit. fig. 20. Plate VII. fig. 4. V. somewhat elongate, divided into two elliptical lobes by a gently sinuous constriction; striz subparallel, fine, granular, about 35 to 40 in ‘001"; inner section ob- scure, linear; median line broad, tapering towards the terminal nodules; central nodule large, orbicular. Hab. Submarine. Glenshira sand and Estuary of the Clyde (Prof. Gregory) ; Estuary of River Coquet, North- umberland (A. S. D.). Navicula Entomon, Ehrenberg. Navicula Entomon, Ehren. Leb. Kr. 1840; Kiitz. Bac. p. 100, t. xxviii. fig. 74; Ralfs, in Prit. Inf. p. 893. Pinnularia Entomon, Ehren. Amer. 1844, t. I. i. figs. 8 & 4; Rabenh. Europ. Diat. p. 218. Diploneis Entomon, Ehren. Mikrogeo. t. xix. fig. 80. Navicula splendida, Greg. Trans. Micr. Soc. n. s. vol. iv. p. 44, pl. v. fig. 14; Ralfs, in Prit. Inf. p. 893; Rabenh. Europ. Diat. p- 204. Plate VII. fig. 5. Frustule large. V. divided by a gentle sinuous constriction F 50 NAVICULEE. into two oblong lobes with rounded or subcuneate obtuse extremities; striz distinctly granular, about 20 in 001", transverse in the middle, oblique towards the extremities, outer band conspicuous, inner faint, linear; central nodule large, bulging. Hab, Salt water. Glenshira sand, Estuary of the Clyde (Prof. Gregory). Cresswell, Northumberland (A. S. D). Navicula Musca, Gregory. Navicula Musca, Greg. Diat. of the Clyde, p. 7, pl. i. fig. 6; Ralfs, in Prit. Inf. p. 893; Rabenh. Europ. Diat. p. 204. Navicula constricta, Grunow, in Wien. Verh. 1860, p. 585, t. i. fig. 18; Rabenh. Europ. Diat. p. 205. Plate VII. fig. 6. Frustule small. V. short, with a sinuous constriction in the middle and cuneate acute, or subacute, extremi- ties; outer section of striz coarse and obscurely granular, about 18 in 001", oblique, inner section obscure; median line broad. The indistinctness of the inner band of strie within the longitudinal intersecting groove gives to this species the appearance of having a marginal band of coarse costate- looking strie. Hab. Salt water. Estuary of the Clyde and Loch Fine (Prof. Gregory). Navicula Bombus, Ehrenberg. Navicula Bombus, Ehren., Kiitz. Spec. Alg. p. 83; Ralfs, in Prit. Inf. p. 893; Greg. Diat. of the Clyde, p. 12, pl.i. fig. 12; Rabenh. Europ. Diat. p. 204. Pinnularia Bombus, Ehren. Berlin. 1844, Diploneis Bombus, Ehren, Mikrogeo. t. xix. fig. 31, NAVICULA DIDYMA. 51 Navicula didyma, Ehren., Sm. Synop. vol. i. pl. xvii. fig. 154a. Forma typica, Rabenh. Europ. Diat. p. 203. New var. Greg. Trans. Micr. Soc. n. s, vol. iv. p. 45, pl. v. fig. 16. Plate VII. figs. 7a & 76. V. divided by a sinuous constriction into two broad, some- what unegual lobes, with subcuneate, or rounded, ex- tremities ; striz radiating, coarsely granular, about 20 in 001"; inner section faint, longitudinal intersect- ing groove incurved; median line broad, tapering towards the terminal nodules. This species is very variable in size and outline, and every degree of gradation between the two forms figured is met with. Hab. Brackish water: common. + Navicula didyma, Ehrenberg. Navicula didyma, Ehren., Kiitz. Bac. p. 100, t. iv. fig. 7, t. xxviii. fig. 75; Ralfs, in Prit. Inf. pl. xv. fig. 12. var. pinnis manifestis, Rabenh. Europ. Diat. p. 208. Pinndlaria didyma, Ehren. Amer. II, iv. fig. 3; Rabenh. Siissw. Diat. p. 46, pl. vi. fig. 26. Diploneis didyma, Ehren. Mikrogeo. t. xix. fig. 32. Plate VII. figs. 8a & 86. V. oblong, slightly constricted in the middle, extremities broadly rounded ; striz subparallel, nearly transverse, coarse, obscurely granular, about 17 in ‘001"; outer section very conspicuous, inner faint and linear. The species originally described and figured by Ehren- berg as Pinnularia didyma seems to have been lost sight of by recent observers, although his description as given by Kiitzing is sufficiently plain (striata, latiuscula, media 52 NAVICULES. leviter constricta, apice late rotundata) ; his figure repre- sents it with parallel strig. More recently, in the ‘ Mikro- geologie,’ he has given a more definite figure, which re- sembles the form selected in the present work to represent N. didyma wore closely than any other with which I am acquainted. In both of Ehrenberg’s figures the strie are parallel, or transverse, and conspicuous. Prof. Smith, in the ‘Synopsis,’ figured two widely different species as ordinary forms of N. didyma,—one being, as he states, N. Apis, Ehren., while the other is evidently the less con- stricted form of N. Bombus, Ehren. Rabenhorst, in 1853 (Siissw. Diat.), appears to have reproduced Ehrenberg’s description and figure ; in his recent work, however (Europ. Diat.), his description of N. didyma is applicable to N. Bombus, Ehren., and certainly not to Ehrenberg’s type of the former, which he has reduced to a mere variety (pinnis manifestis) ; he has also made N. Apis, Ehren., another variety (pinnis subparallelis) . These observations will tend to explain the great confu- sion with which the present species has been surrounded, and the difficulty of ascertaining which is really the original Pin. didyma of Ehrenberg. Hab. Salt or brackish water: frequent. Coast of Nor- thumberland (4. S. D.). NAVICULEA. 53 Section IT. Vatve NARRow, MORE OR LESS CONVEX. It will be observed that the valve, in species typical of Section I. (such as Navicula elliptica or N. pretexta), is much flattened and broad in proportion to its length, so that the entire frustule is very much broader on its S. V. than on its M. V., which is linear and comparatively narrow. In Section II., however, the relative proportions of the valve and of the frustule are entirely reversed (especially in the more typical forms, such as N. Northum- brica and its allies): the former is highly convex and narrow in proportion to its length, while the latter is very much broader on its M. V. than on its S. V. But as these two opposite types of development are receded from in the more aberrant or less typical species, we find the distinctive features of the two sections more and more diminished until they approximate each other very closely. In consequence of this fact an obstacle presents itself to the splitting up of the huge genus Navicula into two distinct genera. However the two primary sections into which I have divided it may be regarded as equivalent to subgenera which gradually approximate to each other, or become almost merged, through the medium of species in which the sectional or subgeneric characters become less and less distinct. Subsection I. Valve highly convex, compressed laterally into a keel elevated towards the extremities and depressed in the middle. Frustule on M. V. broader than on S.V., con- stricted in the middle and expanded towards the extremities. In the peculiar configuration of the valves and of the frustule, the species of this subsection are allied to the genera Amphiprora and Donkinia, between which and the G 54 NAVICULE. Navicule they form a connecting link; they constitute a highly natural group, in which the typical characters of Section II. are most highly developed. A. Valve lanceolate, linear-lanceolate, or linear ; strie conspicuous, costate, or obscurely granular, Navicula Northumbrica, Donkin. Navicula Northumbrica, Quart. Micr. Journ. n.s, vol. i. p. 9, pl. i. fig. 5; Rabenh. Europ. Diat. p. 175. Plate VIII. figs. la & 18. Frustule on M. V. very broad, quadrangular, slightly con- stricted in the middle, central nodules prominent, ex- tremities truncate with slightly rounded angles. V. very narrow, lanceolate, acute; striz transverse, ob- scurely granular, about 28 in ‘001", those opposite the central nodule coarser, opaque, and slightly convergent. The lateral compression of the valve in this species is so great that the distance between the two margins is less than that between the margin and the median line; conse- quently it is difficult to obtain a S. V. of the valve, which generally presents only one of its sides for observation. Hab. Marine. Cresswell, Tynemouth, and other locali- ties on the sandy beach of Northumberland: abundant. Cumbrae, Clyde ; and Teignmouth, 8. Devon (Prof. Walker Arnott). Navicula inflexa, Gregory. Pinnularia infleva, Greg. Trans. Micr. Soc. n.s. vol. iv. p. 48, pl. v. fig. 20; Rabenh. Europ. Diat. p. 218. Navicula inflera, Ralfs, in Prit. Inf. p. 905. Plate VIII. figs. 2a & 20. Frustule small, on M. V. broad, constricted in the middle, NAVICULA CANCELLATA. 55. extremities truncate-rotund. V. lanceolate, subacute, terminal nodules conspicuous ; striz distinct, oblique, connivent, and slightly shortened around the central nodule, reaching to the median line, about 25 in 001". Hab. Marine. Glenshira sand; Estuary of the Clyde (Prof. Gregory) ; Linemouth, coast of Northumberland, abundant (A. S. D.). Navicula longa, Gregory. Pinnularia longa, Greg. Trans, Micr. Soc. n. s, vol. iv. p. 47, pl. v. fig. 18; Rabenh. Europ. Diat. p. 218. Navicula longa, Ralfs, in Prit, Inf. p, 906, Plate VIIL figs. 3a & 36, Frustule much elongated, on M. V, narrow, slightly con- stricted in the middle, angles rounded. V. narrow, lanceolate, acute; strie distant, coarse and costate, about 14 in :001", oblique, reaching to the median line and shortened opposite the central nodule. Hab, Marine. Glenshira sand, Lamlash Bay, Isle of Arran, and Estuary of the Clyde (Prof. Gregory). Navicula cancellata, Donkin. Navicula truncata, Donk. Quart. Micr. Journ. un. s. vol. i. p. 9, pl. i. fig. 4. Pinnularia truncata, Rabenh, Europ. Diat..p. 217. Plate VIII. figs. 4a & 46. Frustule on M. V. broad, oblong, rectangular, constricted in the middle, extremities truncate, angles prominent. V. narrow, linear, or linear-lanceolate, extremities tapering, acute or subacute; strie reaching to the median line, shortened opposite the central nodule, transverse and parallel, coarse and costate, from 14 to 15 in 001". G2 56 NAVICULEA. Hab. Marine. Abundant in sand-gatherings, coast of Northumberland (A. S. D.). Isle of Arran and Estuary of the Clyde (Prof. Gregory). Navicula arenaria, Donkin. Navicula arenaria, Donk. Quart. Mier. Journ. n.s. vol. i. p. 10, pl. i. fig. 9; Rabenh. Europ. Diat. p. 177. Plate VIII. figs. 5a & 58. Frustule on M. V. oblong, slightly constricted in the middle, extremities truncate. V. narrow, lanceolate, slightly constricted near the acute extremities ; strie costate, conspicuous, connivent, reaching to the me- dian line. Hab. Marine. Abundant in sand-gatherings, coast of Northumberland (A. 8. D.). Navicula apiculata, De Brébisson. Navicula apiculata, Bréb, Diat. de Cherb. p. 16, fig. 5; Ralfs, in Prit. Inf. p. 903. Pinnularia rostellata, Greg. Diat. of the Clyde, p. 16, pl. i. fig. 20, Plate VIIL figs. 6a & 66. Frustule on M. V. broad, oblong, constricted in the middle, extremities truncate, angles bevelled. V. linear, con- stricted into tapering, acute apices; strize reaching to the median line, very oblique towards the extremities, transverse opposite the central nodule, costate, some- what distant, about 18 in -001". This species is closely allied to N. cancellata, though smaller ; its frustule on M. V. is easily recognized from that of the latter by the oblique striz curving towards the NAVICULA FORTIS. 57 extremities, instead of appearing as transverse parallel bars. Hab. Marine. Lamlash Bay, Isle of Arran, and Loch Fine (Prof. Gregory) ; coast of Northumberland, plentiful in sand-gatherings (A. S. D.). Navicula minor, Gregory. Navicula minor, Greg. Diat. of the Clyde, p. 5, pl. i. fig. 1; Ralfs, in Prit, Inf, p. 909; Rabenh. Europ. Diat. p.177. Plate VIII. figs. 7@ & 7 6. Frustule small, on M. V. oblong, constricted in the middle, extremities truncate, angles bevelled. V. elliptical, lanceolate, extremities acute, slightly acuminated ; strie oblique, connivent, distinct, 35 in ‘001", some- what shortened in the middle of the valve. Hab. Marine. Loch Fine (Prof. Gregory). Tyne- mouth, Northumberland, frequent in sand-gatherings (A. 8. D.). Navicula fortis, Gregory. Pinnularia fortis, Greg. Trans. Micr. Soc. n. gs. vol. iv. p. 47, pl. v. fig. 19; Rabenh. Europ. Diat. p. 215, Navicula fortis, Ralfs, in Prit. Inf. p. 905. Plate VIIL figs. 8a, 8b, & 8c, Frustule small, on M. V. broad, short, quadrangular, con- stricted in the middle, angles slightly rounded, ex- tremities truncate. V. broadly lanceolate or lozenge- shaped, obtuse; striz reaching to the median line, slightly oblique and connivent, coarse and costate, about 16 in :001". This species is somewhat at variance, in the breadth of 58 NAVICULEZ. its valve, with the characters assigned to Sec. II.; but in other respects it is quite conformable: its valves are highly convex and keeled, and its frustule on M. V. is broad and constricted, showing its proper position to be in the present subsection. Hab. Marine. Tynemouth sands Northumberland, South-Shields sands (A. 8. D.) ; Clyde (Prof. Gregory). B. Valve rhomboid or linear ; stri@ fine, transverse, and parallel, or nearly so, reaching to the median line. Navicula rhombica, Gregory. Navicula rhombica, Greg. Quart. Mier. Journ. vol. iii. p. 40, pl. iv. fig. 16, and Trans. Micr. Soc. n. 8, vol. iv. p. 38, pl. v. fig. 1; Ralfs, in Prit. Inf. p. 908, pl. vii. fig. 71; Rabenh. Europ. Diat. p. 181. Navicula Inbellus, Greg. Diat. of the Clyde, p. 57, pl. vi. fig. 101; Ralts, in Prit, Inf. p. 904; Rabenh. Europ, Diat. p. 172. \ \ Plate IX. figs. la & 16, Frustule on M. V. broad, quadrate, slightly constricted in the middle, angles slightly rounded, extremities trun- cate ; connecting zone traversed by longitudinal lines. V. hyaline, rhombic, or elliptical-lanceolate, with sub- acute or obtuse extremities; striz fine, about 45 in 001", reaching to the median line, nearly transverse, but slightly connivent and more opaque and distinct around the central nodule. Hab. Salt water. Glenshira sand and Tantallon, Had- dingtonshire ; Estuary of the Clyde (Prof. Gregory); New- biggin, Northumberland (A. S. D.). NAVICULA PLICATA. 59 Navicula plicata, Donkin, n. sp. Plate IX. figs. 2a & 2d, Frustule on M. V. broad, oblong, slightly constricted in the middle, extremities truncate, angles slightly rounded, connecting zone traversed by longitudinal lines. V. narrow, linear, extremities tapering, obtuse; striz ‘fine, transverse, reaching to the median line, distinct, above 50 in -001". I discovered this species in great abundance in a living state, in June and July 1869, associated with N. forcipata, N. abrupta, N. humerosa, and other marine species, in sand-gatherings, in a secluded nook on the sea-shore near Warkworth, Northumberland. It is closely allied to N. rhombica, Greg., and to N. Auklandica, Grunow (Wien. Verh. 1863, p. 151, t. xiv. fig 14); it differs from N. rhombica in its longer, much narrower, almost linear valve and tapering obtuse extremities, and in its strie, which are transverse and of uniform distinctness throughout. It resembles N.. Auklandica in size and outline, but differ in having much finer striz and the connecting zone desti- tute of longitudinal rows of nodules. Grunow describes N. Auklandica as having subparallel striz, coarser in the middle of the valve and 36 in 001", the connecting zone as exhibiting longitudinal lines of transversely elongated nodules: he states that it was collected on the sandy beach of the Aukland Islands by De Frauenfeld (Exped. Novara) ; it will be observed, therefore, that the habitat of this species is exactly that of N. plicata. Prof. Gregory doubted whether N. rhombica and his N. Libellus are Navicule, thinking that possibly they might be found to belong to the genus Schizonema : the discovery, however, on the open beach of N. plicata by myself in great abundance in a 60 NAVICULE. free condition, and of N. Auklandica by De Frauenfeld in similar localities, certainly negatives this supposition. Hab. Marine. Warkworth, Northumberland, abundant in sand-gatherings, June and July 1869 (A. S. D.). Navicula simulans, Donkin. Amphiprora constricta, Ehren. Amer. 1844, p. 122, t. I. vi. fig. 28; - Kiitz. Bae. p. 107, t. xxix. fig. 34; Sm. Synop. vol. i. p. 44, pl. xv. fig. 126; Ralfs, in Prit. Inf. p. 922, pl. xii, fig. 1; Rabenh. Europ. Diat. p. 258, Plate IX. figs, 3a & 3 6. Frustule on M.V. oblong, with a sinuous constriction in the middle, extremities truncate, angles gently rounded. V. hyaline, lmear, with cuneate subacute extremi- ties; striz very fine, obscure (68 in ‘00l", Smith), transverse, reaching to the median line, much short- ened opposite the central nodule, so as to leave a transverse median blank space reaching near to the margin. Although this species has hitherto been described as an Amphiprora, it is wanting in the distinctive characters of this latter genus, between which and the Navicule it forms one of the connecting links. It is undoubtedly a Navi- cula, and its proper position in the present subsection, being allied to N. maxima, Greg. Hab. Salt water: frequent. Coast of Sussex (Prof. Smith); Newbiggin, Northumberland (4. S. D.) ; near Hull, common (Mr. Norman). Navicula maxima, Gregory. Navicula maxima, Greg. Quart. Micr. Journ, vol. iii. p. 41, pl. iv. fig. 19, and Trans. Micr. Soc. n. s. vol. iv. p. 89, pl. v. figs. 2, 2**. NAVICULA MAXIMA. Gi Navicula excentrica, Grun. in Wien. Verh. 1860, p. 545, t. i. fig. 1, Navicula bicuneata, Grun. in Wien. Verh. 1860, p. 546, t. i. fig. 4; Rabenh. Europ. Diat. p. 206. Navicula Liber, Smith, var.b. forma major, Rabenh, Europ, Diat. p. 180. Plate IX. fig. 4, Frustule large, on M. V. oblong, constricted in the middle, angles rounded, ends truncate. V. linear, or sublinear with a gentle sinuous constriction in the middle, extre- mities cuneate, obtuse; strie transverse, reaching to the median line, fine, about 45 in -001", crossed by one or two longitudinal lines extending between the apices. Much confusion prevails concerning this species, which was first discovered by Prof. Gregory in the Glenshira sand, and described in his papers on this deposit (Joc. cit.) ; un- fortunately, he subsequently described and figured N. Liber, Sm., as the typical N. maxima, and reduced the original form which he had so named to a variety. Grunow in 1860 (op. cit.) made two new species of Gregory’s original N. maxima ; these he named N. excentrica and N. bicuneata ; but afterwards, in 1863, he reduced them to synonyms of N. Liber, the striz of which he estimates at from 40 to 52 in :001"—a range of variation, however, which certainly does not prevail in any known species. Rabenhorst (op. cit.) retained Grunow’s N. bicuneata, but referred his N. excentrica to N. Liber, as a large variety (forma major), notwithstanding the authority of the latter that both are identical. The specimen figured in the present work is from the estuary of the Clyde, and supplied to me by the late Prof. Gregory. Hab. Marine. Glenshira sand, Lamlash Bay, Isle of Arran, and Estuary of the Clyde (Prof. Gregory). This species also occurs in the Mediterranean and Adriatic. 62 NAVICULEX. Navicula Liber, Smith. Navicula Liber, Sm. Synop. vol. i. p. 48, pl. xvi. fig. 183; Ralfs, in Prit. ; Inf. p. 907; Rabenh. Europ. Diat. p. 180. Navicula maxima, Greg. Diat. of the Clyde, p. 15, pl. i. fig.18; Rabenh. Europ. Diat. p.172; Ralfs, in Prit. Inf. p. 909, pl. vii. fig. 75. Navicula linearis, Grun. in Wien. Verh. 1860, p. 546, t. i. fig. 2; Rabenh. Europ. Diat. p. 180. ; Plate IX. figs. 5a & 56. Frustule much elongated, on M. V. rectangular, slightly constricted in the middle, angles bevelled. V. linear, with rounded extremities; strice reaching to the median line, transverse, very fine, above 50 in -001"; dry valve straw-coloured. Distinguished from N. maxima by its smaller size, narrower valve, rounded extremities, curved median line, and finer strie, and by the much more prominent angles and less deeply constricted sides of the frustule on M.V. Hab. Marine: frequent. Coast of Sussex (Prof. Smith); Loch Fine (Prof. Gregory); coast of Northumberland, frequent in sand-gatherings (A. S. D.). C. V. linear-lanceolate ; strie oblique, distinct, and granular. Navicula aspera, Ehrenberg. Stauroptera aspera, Ehren. Amer. p. 184, t. I. i. fig. 12, iii. figs. 1 & 2, II. vi. fig. 20, III. vii. fig. 26, and IV. iv. fig. 1, Mikrogeo. t. xix. fig. 26; Rabenh, Siissw. Diat. p. 49, t. ix. fig. 1. Frustulia fulva, Bréb. in Herb. Binder. Stauroneis aspera, Kiitz. Bac. p. 106, t. xxix. fig. 12; Ralfs, in Prit. Inf. p.914; Rabenh. Europ. Diat. p. 250. Stauroptera Achnanthes, Ehren. Amer. p. 135, t. IIL. iii. fig. 7, and VI. iil. fig. 2, Mikrogeo. pl. XVIL, i. fig. 10; Rabenh. Siissw. Diat. p. 49, t. ix. fig. 2, Stauroneis Achnunthes, Kiitz. Bac. p. 106, t. xxix. figs. 20 & 22; Ralfs, in Prit. Inf. p. 913; Rabenh. Europ. Diat. p. 248. Stauronets pulchella, Sm. Synop. vol. i. p. 61, pl. xix. fig. 194; Ralfs, in NAVICULA CLEPSYDRA. 68 Prit. Inf. p. 914, pl. vii. fig.77; Rabenh. Europ. Diat. p. 251; Heib. Cons, p. 84. n. 6. Plate X. figs. la, 1b, & le. Frustule large, elongated, on M. V. oblong, constricted in the middle, angles much rounded, extremities truncate. V. linear-lanceolate or elliptical-lanceolate, with ob- tuse or subacute extremities ; striz oblique, distinct, and granular, 20 in 001", reaching to the median line, much shortened (so as to form a narrow, linear, marginal hand, and to leave a cuneiform blank space) opposite the central nodule. Dry valve tawny-co- loured. ., This species, originally placed by Ehrenberg in his genus Stauroptera, and afterwards by Kiitzing and subsequent observers in the genus Stauroneis, is a genuine Navicula, and so closely allied to N. Clepsydra, Donk., that to place these two species in different genera would be a violation of correct classification ; the proper position for both forms is in the present subsection. Prof. Walker Arnott (Quart. Mier. Journ. vol. vii. p. 176) correctly pointed out that the striation in both species is different from what is usually observed in the genus Stauroneis. N. aspera is very variable in size, the small variety figured being evidently the Stawroptera Achnanthes of Ehrenberg. Hab. Marine: frequent in rocky pools, and generally distributed. Navicula Clepsydra, Donkin. Navicula Clepsydra, Donk. Quart. Micr. Journ. n. s. vol. i. p. 8, pl. i. fig. 3; Rabenh. Europ. Diat. p. 181. Plate X. figs. 2a & 26. Frustule large, elongated, on M. V. broad, quadrangular, 64 NAVICULE. constricted in the middle, angles prominent, extremi- ties truncate. V. linear-lanceolate or linear-elliptical, with rounded extremities; striz oblique, granular, distinct, 25 in ‘001", reaching to the median line, much shortened (so as to leave an imperfectly orbi- cular blank space) around the central nodule ; colour of dry valve bluish green. This species differs from N. aspera in the colour, outline, and much greater convexity of the valve, in the finer strie and the orbicular shape of the blank space around the cen- tral nodule, in the angles of the frustule on M. V. being pro- minent and sharp, and the middle more deeply constricted ; it differs also in its habitat, which is the sandy beach. Hab. Marine: in sand-gatherings frequent, and occa- sionally quite pure and abundant. Cresswell, Boulmar, Newbiggin, and Tynemouth sands, Northumberland, South- Shields sands, Durham (4. S. D.). D. Valve linear, with rounded extremities ; striae coarse and costate. * Not inflated in the middle. Navicula retusa, De Brébisson. Naviula retusa, Bréb. Diat. de Cherb. p. 16, fig.6; Sm. Synop. vol. ii. p. 92; Ralfs, in Prit. Inf. p. 908; Donk. in Quart. Micr. Journ. ns. Vol.i. p. 14, pli. fig.17; Rabenh. Europ. Diat. p. 186. Navicula pectinalis, Bréb. Sm. Synop. vol. ii. p. 91; Ralfs, in Prit. Inf. p. 909; Rabenh. Europ. Diat. p. 186. Plate X. figs. 3a & 3. Frustule small, on M. V. oblong, constricted in the middle, angles rounded, extremities truncate. V. narrow, linear, with rounded extremities ; stria not reaching to the median line, nearly transverse, distant, coarse, and costate, 20 in ‘O01". NAVICULA CRUCIFORMIS. 65 I have been induced to reduce N. pectinalis, Bréb., of Smith’s Synop. to a synonym of N. retusa, Bréb., because the valve of the latter corresponds with Smith’s description of that of the former, which does not accord with any other allied species, and because of the following observation of Prof. Walker Arnott on the subject :—“It is not to me quite clear on what De Brébisson originally bestowed the name of N. pectinalis; what Smith received from him and sup- posed to be so, I have reason to think was N. retusa, of which Smith only knew the F. V.; and in that state it is almost undistinguishable from N. pectinalis of the Synopsis” (Quart. Micr. Journ. vol. vii. p. 176). Hab. Marine: frequent in sand-gatherings near estua- ries. + More or less inflated in the middle. Navicula cruciformis, Donkin. Navicula cruciformis, Donk. Quart. Micr. Journ. n. 8. vol. i. p. 10, pl. i. fig. 7. Pinnularia Brébissonit, var. d, Rabenh. Europ. Diat. p. 222, Plate X. fig. 4. Frustule on M. V. broad, oblong, quadrangular, constricted in the middle, angles bevelled. V. linear, slightly inflated in the middle, extremities rounded; striz reaching to the median line, very oblique, and diver- ging midway between the central and terminal nodules, costate, 30 in -00L", absent (so as to leave a broad cuneiform blank space) opposite the central nodule ; dry valve brown-coloured. Rabenhorst has referred this species to N. Brébissonii as a variety, forgetting that I described it as being a marine 66 NAVICULEE. form ; moreover it differs essentially in the structure of the valve and in the contour of the frustule on M. V. from N. Brébissonii, which in this aspect is linear, not constricted, and narrower. Hab. Marine. Coast of Northumberland, common in sand-gatherings (A. S. D.). Navicula rectangulata, Gregory. Navicula rectangulata, Greg. Diat. of the Clyde, p.7, pli. fig.7; Ralfs, in Prit. Inf. p. 907. Pinnularia rectangulata, Rabenh. Europ. Diat. p. 215, Plate X. fig. 5. Frustule on M. V. oblong, constricted in the middle, extre- mities truncate, angles bevelled. VV. linear, bulging in the middle and near the broadly rounded extre- mities ; strie reaching to the median line, slightly shortened around the central nodule, oblique, di- verging midway between the central and terminal nodules, distinct, costate, 20 in :001”. Hab. Marine. Lamlash Bay, Isle of Arran (Prof. Gre- gory); coast of Northumberland, common in sand-gather- ings (A. S. D.); New Brighton sands and Leasowe sands, near Liverpool (Mr. Comber). Navicula Trevelyana, Donkin. Navicula Trerelyana, Donk. Quart. Mier. Journ. n. s, vol. i. p. 8, pl. i. eos Sate Rabenh. Europ. Diat. p. 210. Plate X. figs. 6a & 63. Frustule elongated, on M. V. broad, oblong, deeply con- stricted in the middle, extremities truncate, angles NAVICULA HUMILIS. 67 rounded. V. linear, slightly dilated at the middle and near the rounded extremities; striz coarse, costate, very oblique, diverging midway between the central and terminal nodules, reaching to the median line, much shortened around the central nodule, so as to leave a large orbicular median blank space, 25 in 001". This large and beautiful species is readily distinguished from N. rectangulata, Greg., by its larger size, more oblique striz, and large orbicular blank space around the central nodule, and more especially by the peculiarly curved appear- ance imparted to the median line by the great convexity of the valve near the extremities, and its depression in the middle; it was discovered by me at Cresswell, North- umberland, in June 1857, and dedicated to my friend Sir W. C. Trevelyan, Bart., of Nettlecombe, Somersetshire, and of Wallington, Northumberland. Hab. Marine. Cresswell, Linemouth, and Boulmar, Northumberland, frequent in sand-gatherings (A. S. D.). Navicula humilis, Donkin, n. sp. Navicula varians, var., Greg. Trans. Micr. Soc. n. 8, vol. iii, pl. ii, figs. 20 & 208. Navicula inflata, var., Greg. Trans. Mier, Soc. n. 8, vol. iii. pl. ii. fig, 20. Plate X. figs. 7a & 70. Frustule minute, on M.V. broad, quadrate, constricted in the middle, extremities rotund-truncate, angles pro- minent, central nodules projecting. VV. linear, much inflated in the middle, extremities broadly rounded and tumid; strie reaching to the median line, con- vergent, coarse, costate, and very conspicuous. This is the only freshwater species with which I am 68 NAVICULE. acquainted belonging to the present subsection. Prof. Gregory has given three figures of the S.V., which he regarded as var. of N. inflata and of his N. varians ; he appears, however, to have been unacquainted with the highly convex and keeled characters of the valve, and with the contour of the frustule on M. V., features which undoubt- edly establish its position in this subsection. Hab. Fresh water. River Coquet and Sweethope Lough, Northumberland (4. S. D.) ; Scotland (Prof. Gregory). Subsection II. Valve moderately convex, not compressed laterally into a keel; frustule on M. V. linear, not constricted in the middle, and of equal or nearly equal breadth with the S. V. A. Valve linear, dilated in the middle, * Strie oblique, connivent. Navicula nobilis, Ehrenberg. Pinnularia nobilis, Ehren. Berl. 1840, p. 20; Rabenh. Siissw. Diat. p. 44, t. vi. fig. 2, Europ. Diat. p. 209; Sm. Synop. vol. i. p. 54, pl. xvii. fig. 161. Navicula nobilis, Kiitz. Bac. p. 98, t. iv. fig. 24; Ralfs, in Prit. Inf p- 895. Pinnularia mesogongyla, Ehren. Mikrogeo. t. VI. i. fig. 5. Plate XI. fig. 1. Frustule very large, elongated. V. broad, linear, slightly bulging in the middle and at the extremities; striz not reaching to the median line, stout, costate, obliquely inclined towards the central nodule, 13 in O01". Hab. Fresh water: common in boggy pools and ditches in hilly and upland districts. Lough-Mourne deposit, Dolgelly earth, &c. NAVICULA MAJOR. 69 Navicula gentilis, Donkin, n. sp. Navicula major, var. b. crassa, Bréb. in Rabenh. Alg. n. 683; Europ. Diat, p. 210? Plate XII. fig. 1. Frustule large, elongated. V. linear, slightly bulging in the middle and expanding towards the broadly rounded clavate extremities; stricee not reaching to the median line, strongly costate and obliquely inclined towards the central and terminal nodules, 18 in :001". This species is quite distinct from N. nobilis, which it resembles, being very much smaller, proportionally broader at the extremities, and having much finer striz. Nevertheless it appears to have been confounded with the latter species and with N. major. Hab. Fresh water: frequent. In hilly districts: Che- viots, Northumberland ; Lough-Mourne deposit, &c. Navicula major, Kiitzing. Navicula major, Kiitz. Bac. p. 97, t. iv. figs. 19 & 20; Ralfs, in Prit. Inf. p. 896, pl. vii. fig. 65. Bacillaria fulva, Nitzsch (ex parte), t. ii. figs. 13 & 17, 1817. Frustulia major, Kiitz. Syn. p. 19, fig. 25, 1838. Navicula viridis, Ehren. in Pogg. Ann. 1836, t. iii, fig. 1, Inf. 1838, t. xiii. fig. 16, t. xxi. fig. 12; Baily, in Amer. Journ. Jan, 1832, pl. ii. figs. 16 & 17. Pinnularia viridis, Ehren. Amer. 1848, t. I. i. fig. 7, iii. fig. 3, iv. fig. 3, t. II. i. fig. 22, iii. fig. 1, v. fig. 2, vi. fig. 21, t. TIL. i. figs. 1 & 2. Pinnularia major, Rabenh, Siissw. Diat. p. 42, t. vi. fig. 5, Alg. n. 621 & 1485, and Europ. Diat. p. 210; Sm. Synop. vol. i. p. 54, pl. xviii. fig. 162. Plate XI. figs. 2a & 20. Frustule large, elongated. V. broadly linear, turgid in the middle; extremities gently and gradually round- ed; striz not reaching to the median line, strongly H 70 NAVICULER. costate, convergent around the central nodule, 18 in 001". Hab. Fresh water : common in lakes, ponds, and ditches, Loch-Oich deposit, abundant. This species is much more lacustrine in its habitat than the two preceding species. Navicula Tabellaria, Ehrenberg. Pinnularia Tabellaria, Ehren. Amer. t. IL, i. fig. 26, II. i. fig. 7, iii. fig. 6, iv. fig. 5, IV. i. fig. 4. : Pinnularia acrospheria, Rabenh, Siissw. Diat. p. 45, t. vi. fig. 36, Pinnularia leptogongyla, Ehren, Mikrogeo. figg. permult; Rabenh, Europ. Diat. p. 188, Navicula leptogongyla, Ehren. Amer. 1848, p. 180. Navicula acrospheria, Kiitz. Bac. p. 97, t. 5. fig. 2; Ralfs, in Prit, Inf. p- 896. Plate XII. fig. 4. Frustule smallish, elongated. V. rather narrow, linear, slightly bulging in the middle and gently rounded at the extremities ; strize reaching near to the median line, obliquely inclined and gradually shortened around the central nodule, 22 in -001". This is the Pinnularia Tabellaria of Ehrenb. and the Navicula acrospheria of Kiitzing, concerning both of which species the greatest confusion has prevailed. (See Note to Nav. acrospheria). Hab, Fresh water, frequent in hilly and mountainous districts. Cheviots, Northumberland (4. S. D.); Scot- tish Highlands. ‘Loch-Oich deposit, Lough-Mourne de- posit, &e. Navicula gibba, Ehrenberg. Stauroptera gibba, Ehren. Amer. p. 135, t. 1. ii. fig. 3; Rabenh., Siissw. Diat. p. 49, t. ix. fig. 3. Stauroneis gibba, Kiitz. Bac. p. 107, t. xxix. fig. 24; Ralfs, in Prit. Inf p. 914. NAVICULA LATA. 71 Pinnularia gibba, Sm. Synop. vol. i. p. 58, pl. xix. fig. 180 ? Pinndaria Tabellaria, Sm. Synop. vol. i. p. 58, pl. xix. fig. 181 P Plate XII. fig. 3. Frustule of median size, elongated. V. narrowish, linear, bulging in the middle and at the rounded extremities : striz not reaching to the median line, much shortened and often interrupted on one side of the central nodule, very oblique, subdistant, stout and costate, 23 in 001". Hab. Fresh water, frequent in boggy pools in elevated and hilly districts. Loch-Oich deposit, Lough-Mourne deposit, Premnay Peat, &c. Navicula lata, De Brébisson. Navicula lata, Bréb. Considér. sur les Diatom. 18388, p. 18; Kiitz. Sp. Alg. p. 79; Ralfs, in Prit. Inf. p. 908. Pinndaria lata, 8m. Synop. vol. i. p. 55, pl. xviii. fig. 167; Rabenh. Europ. Diat. p. 212, and Siissw. Diat. p. 42. Pinnularia pachyptera, Ehren. Amer. 1844, p. 183, t. IV. ii. fig. 9; Rabenh. Siissw. Diat. p. 45, t. vi. fig. 11. Navicula pachyptera, Kiitz. Bac. p. 98, t. xxviii. fig. 58; Ralfs, in Prit. Inf. p. 896. Pinnularia megaloptera, Ehren. Mikrogeo. t. IIL. i. fig. 4; Greg. Quart. Micr. Journ. vol. iv. p. 3, pl. i. fig. 6. Navicula Suecica, Ehren. Inf. 1888, p. 189, t. xxi. fig. 18; Kiitz. Bac, p- 96, t. xxi. fig. 16; Ralfs, in Prit. Inf. p. 908. Pinnularvia Suecica, Ehren, Mikrogeo. ; Rabenh. Siissw. Diat. p. 42, t. vi. fig. 14. Plate XIII. figs. la & 18. Frustule short, oblong. V. broad linear, slightly dilated in the middle, and broadly rounded at the extremities (in short specimens elliptical or linear-elliptical) ; strize not reaching to the median line, much shortened and connivent around the central nodule, distant, broad and costate, 8 in ‘O01". This species is very variable in size and outline, the H2 72 NAVICULES. short elliptical form being the Pinnularia Suecica of Eh- renberg. Hab. Fresh water. Frequent in hilly and subalpine localities in England, Scotland, and Ireland. + Strie parallel, transverse. Navicula acrospheria, De Brébisson. Frustulia acrospheria, Bréb. Considér. sur les Diatom. p. 19, 1838. Navicula Tabellaria, Kiitz. Bac. p. 98, t. xxviii. figs. 79 & 80, t. xxx. fig. 20; Ralfs, in Prit. Inf. p. 896, pl. xii. fig. 21. Pinnularia Tabellaria, Ehren. ; Rabenh. Siissw. Diat. p.44, t. vi. fig. 24, and Europ. Diat. p. 211; var, acrospheria, Rabenh. Europ. Diat. p. 21]. Pinnularia acrospheria, 8m. Synop. vol. i. p. 58, pl. xix. fig. 183, Navicula punctata, Bréb. Journ. of Quekett Micr. Club, Apr. 1870. Pinnularia gibba, Rabenh, Siissw. Diat. t. vi. fig. 27 a. Pinnularia gibberula, Rabenh. Siissw. Diat. p. 45, t. vi. fig. 30. Plate XII. fig. 2, Frustule smallish, oblong. V. broadly linear, dilated in the middle and at the broadly rounded extremities ; strie short, not reaching to the median line, distinct, costate, subdistant, parallel and transverse, 26 in‘001"; surface of the valve irregularly granular. The short transverse strie and the mottled appearance of the valve at once distinguish this species from its con- geners. In describing it under the name of N. punctaia, at the suggestion of the late Prof. Walker Arnott, De Brébisson observes (op. cit. supra) :—“ It is this species to which I had in 1838 given the name of Frustulia acrosphe- ria; but it is not the Navicula acrospheria of Kiitzing, the summits of which are not sensibly enlarged—nor, as some authors have thought,the Navicula Tabellaria of Ehrenberg, which.has no punctuations.” To avoid confusion, I have adopted the original specific name of De Brébisson. NAVICULA LIMOSA. 73 Navicula scopulorum, De Brébisson. Navicula scopulorum, Bréb. in Kiitz, Spec. Alg. p.81; Ralfs, in Prit. Inf. p. 895; Rabenh. Siissw. Diat. p. 41, t. v. fig. 7. Navicula mesotyla, Ehren. Amer. 1843, p. 180; Kiitz. Bac. p. 99, t. v. fig. 3, and t. xxviii. fig. 84; Rabenh. Siissw. Diat. p. 41, t. v. fig. 6 P Pinnularia Johnsonit, Sm. Synop. vol. i. p. 58, pl. xix. fig. 179; Rabenh. Europ. Diat. p. 211. Plate XII. fig. 5 Frustule much elongated, slender. V. narrow, linear, in- flated in the middle and at the rounded extremities ; striz reaching to the median line, parallel, transverse, faint, 56 in ‘001"; colour of dry valve brownish. Hab. Brackish water. Pilling near Lancaster (Mr. Johnson, Feb. 1851). Shoreham, Sussex, March, 1851 (Prof. Smith). Piers, Victoria Dock, Hull, and Lagoon, Grimsby (Mr. Norman) ; Bootle shore near Liverpool (Mr. Comber). Navicula limosa, Kiitzing. Navicula limosa, Kitz. Bac. p. 101, t. iii. fig. 50; Rabenh, Siissw. Diat. p. 41, t. vi. fig. 31, and Europ. Diat. p. 188; Ralfs, in Prit. Inf. p. 894; var, inflata, Grunow, in Wien. Verh. 1860, p. 544, t. iil. fig. 8¢.; and var. bicuneata, Grunow, in Wien. Verh. 1860, p. 544, t. iii. fig. 7. Navicula gibberula, Kitkz, Bae. p. 101, t. iii. fig. 50*; Sm. Synop. vol. i, p. 51, pl. xvii. fig. 160; Ralfs, i in Prit, Ink p. 895. Navicula leptogongyla, Ehren. ; Kiitz, Bae. p. 99, t. iv. fig. 9; Rabenh. Siissw. Diat. p. 41, i v. fig. 8 Navicula tumidula, Rabenh. Siissw. Diat. p. 41, t. v. fig. 9, and Europ. Diat. p. 188; Ralfs, in Prit. Inf. p. 895, Navicula Silicula, Ehren. Amer. p. 181. n. 161, Mikrogeo. fig. numer. ; Kiitz. Bae. p.101; Ralfs, in Prit. Inf. p. 894 ; Rabenh. Siisew. Diat. p. 41, and Europ. Diat. p. 206. Plate XII. figs. 6a & 66. Frustule small, oblong. V. highly convex, narrow, linear, 4. NAVICULEZ. with a central and terminal inflations, extremities cuneate and subacute, or rounded ; striz reaching to the median line, transverse, fine and delicate; dry valve yellowish brown. The great variation im size and outline to which this species is subject has caused it to be described under the various synonyms given above. Kiitzing seems to have relied on size and outline in separating N. gibberula as a species distinct from N. limosa. Hab. Fresh water: common and very generally distri- buted. Navicula ventricosa, Ehrenberg. Navicula ventricosa, Ehren. Kreidethierchen, 1839, t. iv. fig. 10; Kiitz. Bac. p. 99, t. xxi. fig. 15. Plate XII. fig. 7. Frustule small, oblong. V. highly convex, linear, inflated in the middle ; extremities slightly tumid and rounded ; striz reaching to the median line, transverse, fine and delicate, absent opposite the central nodule. This species is distinguished from the preceding, with which it has evidently been confounded, by its smaller size and the blank unstriated space opposite the central nodule. It agrees with the figure of N. ventricosa, Ehren. given by Kiitzing, to which I have referred it, to prevent the intro- duction of a new name. Had. Fresh water: frequent in elevated situations. Sweethope Lough, Northumberland ; Loch-Oich deposit. PLATE J. [All the Figures in the work are magnified 500 diameters, unless it is specially stated to the contrary. ] Fig. 1. Navicuta ayauina, Donkin. 2. Navicua LitroRaLis, Donkin. 8. Navicu.a astiva, Donkin. 4. Navicuna Smirait, De Brébisson. 5. Navicuxa rusca, Gregory. 6a & 66. Navicuts exviiprica, Kiitzing. 7. Navicuna nitgscens, Gregory. 8. Navicuna Lingata, Donkin. 9. NAVICULA SUBORBICULARIS, Gregory. 10. Navicuta pyemaa, Kiitzing. PLATE 1. Tuffen West.adnat London, Published ‘ay Jc ohn Van Voorst,Paternoster Pow: Fig. 1. CaN aa bh w PLATE II. Navicuna Pr&texta, Ehrenberg. NavicuLa NEBULOSA, Gregory. Navicuta Hennepyit, Smith. Navicuxa rorcrpata, Greville. NavIcuLa SPECTABILIS, Gregory. NavicuLa aprupta, Gregory. Navicuta tyra, Ehrenberg. Navicura ciavata, Gregory. Navicuta Rostrata, Ehrenberg. PLATEN es bee te 2 & ce ob “o? ees, 352, "3,026.6 Sgababe: es oko London ‘Pubhshed by John Van Voorst, Paternoster Row. St, ad nat, Tuffen We. PLATE III. Fig. 1. Navicuta eranutata, De Brébisson. 2. NavicuLa Latissima, Gregory. 3. Navicuta HUMEROSA, De Brébisson. 4, NavicuLa BREVIS, Gregory. 5. Navicuna marina, Ralfs. 6a & &. Navicuta pusiLLa, Smith. 7. Navicuta Carassius, Ehrenberg. 8. Navicuta Semen, Ehrenberg. 9. Navicuca inFiata, Kiitzing. 10. Navicuta Gastrum, Ehrenberg. 11. NavicuLa cocconEIFormis, Gregory. 12. Navicuta HERES, Ralfs. London, Published byJ ohn Van Voorst Paternoster Row. Tuffen West ad nat Fig. 1. > N@ gr PLATE IV. NavicuLa ELEGANS, Smith. . Navicuza supsatina, Donkin. NavicuLaA PALPEBRALIS, De Brébisson. a, the typical form; 4, var. in which the median blank space is lanceolate, and the striee opposite the central nodule slightly shortened. NavicuLa aANGULOosA, Gregory. NavicuLa sEMIPLENA, Greville. NavicuLa alpina, Smith. a,8.V.; 6, M.V. NavicuLa LatiuscuLa, Kiitzing. PLATE Iv. sa ii cau (C— ae — Vio ny uo oan ala PUN QOGHOEODESSUPNIDESEO ET PEED ROTO DUD WOpbeneaeUAROUAC LEAH RIL sSoetHoaOL — MUNROE ‘Tuffen West ad nat, ‘London, Published. by Jobn Van Voorst,Paternoster Row PLATE V. Fig. 1. Navicuta macutosa, Donkin. 2. NavicuLa Lavissima, Kiitzing. . NavicuLa DIRHYNcHUSs, Ehrenberg. 3 4, Navicuta Hircucocku, Ehrenberg. 5. Navicuta pusia, Ehrenberg. 6 . Navicuta Iripis, Ehrenberg. ~ . Navicuna Firma, Kiitzing. 8. Navicuta arrinis, Ehrenberg. 9, NavicuLa AMPHIRHYNCcHUS, Ehrenberg. 10. NavicuLa sPH#RoPHORA, Kiitzing. lla &116. Navicuta ANGLICA, Ralfs. 12, Navicuta punctata, Kiitzing. 18. Navicuta AmpuisBzna, Bory de St. Vincent. 14, Navicuna cryprocerHaLa, Kiitzing. BV m1 fan Joorst Paternoster how, ou London Publisnea by Geo West adnat.sc. PLATE VI. . Navicuna unposa, Ehrenberg. Navicuna incurva, Gregory. . Navicua Binopis, Ehrenberg. . NavicuLa RHYNCHOCEPHALA, Kiitzing. NavicuLa amBicua, Ehrenberg. . Navicuna cuspipara, Kiitzing. Navicuta Rosretium, Smith. NavicuLa IntEGRA, Smith. . Navicuta rutva, Nitzsch. Navicua sERians, De Brébisson. NavicuLa RHomBorpEs, Ehrenberg. NavicULs CRASSINERVIA, De Brébisson. Navicuna VENETA, Kiitzing. Navicuta Crucicuta, Smith. Navicuta Fouzis, Ehrenberg. PLATE VI. (" \ \ GeaWest.ad nat se London, Pubhshed. by John Van Voorst Paternoster Row. N QAP OW PLATE VII. . Navicuta Cragpro, Ehrenberg. a, the typical form, from the coast of Northumberland ; b, short var., from the estuary of the Clyde. . Navicuna IntERRUPTA, Kiitzing. Navicuua Aris, Ehrenberg. Navicuxa tncurvata, Gregory. Navicuta Entomon, Ehrenberg. Navicuta Musca, Gregory. . Navicuta Bompvus, Ehrenberg. a, the typical form, from the estuary of the Clyde; 4, the less-constricted var., from the coast of North- umberland. 8a & 8b. NavicuLa pipyma, Ehrenberg. PLATE, VL ae ‘ lillie if Secor ax 7 re 99008 O00 COGDIGIAIG OVO vA AMM SH, S38 G0D 090 GOGH 00 SU HOCAIDHOD BAVDDAOOGD0 OND OUOSIRERY i \ Ha London. Pubbshed by John Van Voorst Paternoster Row. Geo West adnat.sc. Fig. 1. ane ww ” PLATE VIII. Navicuta NortHUMBRICA, Donkin. a, S.V.; b, M. V. . Navicuta INFLEXA, Gregory. a,S.V.; 6,M.V. . Navicuta tone@a, Gregory. a,8.V.; 6,M.V. Navicura canceLLata, Donkin. a,S8.V.; 6,M.V. . Navicuna aRENARIA, Donkin. a@,8.V.; 6,M.V. . Navicuta apicutata, De Brébisson. a, S. V.; 6,M.V. Navicuta Minor, Gregory. a,S.V.; 6,M.V. 8. Navicuta rortis, Gregory. a@&0,8.V.; c,M.V. PLATE VII N 8 ESSN EERO OT